Understanding RAM mount parts and how they fit together turns a box of separate aluminum plates, rubber ball studs, and machine screws into one of the most durable modular mounting systems available. Backed by a lifetime structural warranty, the RAM mounting system uses an elastomeric ball-and-socket architecture that lets individual components swap freely across vehicles. A handlebar U-bolt base from your motorcycle can move to a car windshield or truck dashboard simply by pairing your existing double socket arm and device cradle with a new base.
Pictured Kit (RAM-B-138U): Flat Round Base (`RAM-B-202U`) + Medium Arm (`RAM-B-201U`) + Diamond Adapter (`RAM-B-238U`)
1. SURFACE BASE (1″ BALL)
Attaches to your vehicle or panel. Choose a Twist-Lock Suction Cup (`RAM-B-224-1U`) for glass, a U-Bolt (`RAM-B-231ZU`) for bars, or a Round Plate (`RAM-B-202U`) for flat drill-down installs.
2. DOUBLE SOCKET ARM
Clamps over the base ball at one end and the cradle ball at the other. Turning the center flywheel knob on the `RAM-B-201U` locks both sockets simultaneously.
3. CRADLE & BALL ADAPTER PLATE
Holds your device. Phone X-Grips have a 1-inch ball molded into the back. Custom cradles and GPS docks bolt to a 2-hole Diamond Base (`RAM-B-238U`) or 4-hole Round AMPS Plate (`RAM-B-202U`).
Quick Answer: Every standard RAM mount setup uses three matching ball-size components: a surface base, a double socket arm (`RAM-B-201U`), and a device cradle (either with a molded ball or bolted to a `RAM-B-238U` diamond or `RAM-B-202U` round AMPS ball adapter). For a clean RAM mount installation, press the nylock nuts into the recessed hex pockets on the inside face of your cradle, screw the ball adapter plate to the back, seat the base ball and cradle ball into opposite ends of the open socket arm, and tighten the side knob firmly by hand.
Whether you bought a complete kit or are selecting individual RAM mount components for a custom build, this guide walks through how to assemble a RAM mount step by step, explains when your holder needs a two-hole diamond base versus a four-hole AMPS plate, and covers the exact hardware specs for the five core 1-inch (B-size) building blocks. For a full overview of how the catalog scales from phones to marine electronics, visit our complete RAM Mounts system guide.
RAM Mount Parts and Components: How the Three-Part System Works
Every basic RAM mount assembly relies on three core RAM mount parts: a mounting base, a double socket arm, and a device cradle (or ball adapter plate). Knowing the mechanical role of each piece makes RAM mount installation quick and predictable across cars, trucks, motorcycles, and boats.
- 1. The Base: Anchors the mount to your vehicle, handlebar, glass, or flat surface and places a rubber-coated ball stud at the mounting point. Popular base options include the `RAM-B-224-1U` twist-lock suction cup for windshields, the `RAM-B-231ZU` U-bolt clamp for handlebars and rails, and the `RAM-B-202U` pre-drilled round plate for flat-surface bolt-down installs.
- 2. The Double Socket Arm: Connects the base ball to the cradle ball. It uses two opposing aluminum or composite socket halves that clamp over the base ball at one end and the cradle ball at the other. Tightening the center flywheel knob locks both connections simultaneously. See our RAM 1-inch ball arms overview for exact dimensions on short, medium, and long socket arms.
- 3. The Cradle and RAM Mount Ball Adapter: Holds your phone, tablet, GPS, or radio. Universal phone holders like the standard X-Grip have a 1-inch ball molded directly into the back, whereas custom cradles and factory GPS brackets require a separate two-hole diamond adapter (`RAM-B-238U`) or four-hole round AMPS adapter (`RAM-B-202U`) bolted to the rear housing.
Important: RAM Mounts are made in several ball diameters. The most popular size for phones, action cameras, and automotive or motorcycle GPS units is the B-Size (1-inch ball), while heavier tablets and marine chartplotters step up to the C-Size (1.5-inch ball) or D-Size (2.25-inch ball). All three parts in your setup must share the exact same ball size. If you are ordering individual components, check their part-number size letters in our RAM mount ball sizes guide before buying.
Core 1-Inch (B-Size) RAM Mount Parts List
If you are piecing together a 1-inch B-size setup or replacing a single component to move your mount into a second vehicle, the table below compares the five foundational RAM mount parts used in most car, truck, motorcycle, and GPS builds.
| Component (Part Number) | Fits / Attachment | Best For |
|---|---|---|
| RAM 3.3″ Twist-Lock Suction Cup Base (RAM-B-224-1U) | 3.3-inch vacuum suction pad with cam lever and 1-inch B-size ball | Car windshields, truck glass, aircraft windows, and non-porous flat surfaces |
| RAM Handlebar U-Bolt Base (RAM-B-231ZU) | Zinc-coated U-bolts for 0.50-inch to 1.25-inch round bars with 1-inch ball | Motorcycle handlebars, adventure GPS crossbars, ATVs, and tubular rails |
| RAM Diamond Ball Base (RAM-B-238U) | 2.43″ x 1.31″ diamond plate with 2-hole AMPS pattern (1.912″ hole spacing) | 2-hole RAM custom cradles, Garmin Spine clips, and compact device holders |
| RAM 2.5″ Round AMPS Ball Plate (RAM-B-202U) | 2.5-inch round plate with 4-hole AMPS pattern (1.181″ x 1.496″) and 1-inch ball | 4-hole GPS docks (Garmin Zumo, TomTom), tablet X-Grips, or flat drill-down bases |
| RAM Medium Double Socket Arm (RAM-B-201U) | 3.69-inch overall length (3.0-inch socket-to-socket) for 1-inch B-size balls | Connecting any B-size base ball to any B-size cradle ball across vehicles |
Step 1: Choosing and Installing Your RAM Base
Every RAM mount installation begins at the mounting surface. Because all 1-inch B-size components share the exact same ball diameter, you can keep dedicated bases installed in your car, truck, and motorcycle and move your arm and cradle between them in seconds. Here are the instructions for the three most common base styles.
1. RAM Twist-Lock Suction Cup Base (RAM-B-224-1U) for Windshields
The RAM 3.3-Inch Twist-Lock Suction Cup Base (`RAM-B-224-1U`) is the most popular removable base for automotive windshields, truck glass, and non-porous flat surfaces. It pairs a 3.3-inch elastomer vacuum pad and mechanical cam-locking ring with an integrated `RAM-B-238U` 1-inch ball plate.
If your suction cup arrived with its diamond ball plate unattached in the package, line up the two holes in the aluminum diamond plate with the two threaded bosses in the center of the plastic suction housing and tighten the two included coarse-thread Phillips screws until snug. Wipe both the glass windshield and the rubber suction pad with isopropyl alcohol and let them dry. Twist the outer locking lever counterclockwise to its unlocked stop, press the center of the suction cup firmly against the glass to expel trapped air, and rotate the locking lever clockwise until it snaps into place.
2. RAM Handlebar U-Bolt Base (RAM-B-231ZU) for Motorcycles and Rails
The RAM Handlebar U-Bolt Mounting Base (`RAM-B-231ZU`) is the standard clamp base for round bars, rails, and motorcycle or bicycle handlebars measuring 0.50 inches to 1.25 inches in diameter. The hardware packet includes a powder-coated aluminum 1-inch ball saddle, two zinc-coated steel U-bolts of different diameters, two 1/4″-20 nylock nuts, two black rubber thread caps, and a curved composite reducer shim.
To install the `RAM-B-231ZU`, select the U-bolt that matches your handlebar tube. If you are mounting to a narrow 0.50-inch (12mm) adventure-bike GPS crossbar or mirror stem, snap the black composite shim over the bar first so the U-bolt does not run out of threads before clamping tight. Wrap the U-bolt around the bar, slide the aluminum ball saddle over the two threaded legs, and start both nylock nuts by hand. Using a 7/16-inch wrench or deep socket, tighten the left and right nuts alternately a few turns at a time so the gap stays symmetrical on both sides. Once the base cannot twist on the handlebar, press the black rubber caps over the exposed bolt tips.
3. Flat-Surface Drill-Down Bases for Dashboards, Consoles, and Boats
For permanent bolt-down installations in commercial trucks, fleet vehicles, workbenches, or boats, a flat-surface base bolts directly through the mounting surface. In the 1-inch B-size catalog, the RAM 2.5-Inch Round Plate (`RAM-B-202U`) works as both a four-hole cradle adapter plate and a heavy-duty flat-surface drill-down base. Because dash and console thicknesses vary widely, RAM does not bundle surface-mounting screws with bare drill-down plates. Always inspect behind the panel for wiring looms or airbags before drilling, and back up thin plastic or fiberglass panels with stainless machine screws, fender washers, and nylock nuts. See our RAM flat surface mounts guide for detailed drill-down hardware setups.
Step 2: Choosing and Assembling Your Cradle and Ball Adapter Plate
Before your device holder can connect to the double socket arm, it needs a 1-inch rubber ball on the back. RAM cradles fall into two groups depending on whether that ball is molded into the holder or bolted on using a separate RAM mount ball adapter.
Universal Phone Cradles vs. Tablet X-Grip Cradles
Universal phone holders like the standard and large RAM X-Grip phone cradles (`RAM-HOL-UN7BU` and `RAM-HOL-UN10BU`) have a 1-inch B-size rubber ball permanently molded into the back of the composite housing. No screwdriver or adapter plate is needed: push the rubber grip caps onto the four stainless steel arms (using a drop of the included super glue inside each cap for open-cockpit motorcycle use) and pop the rear ball directly into your socket arm.
Keep in mind that tablet-sized X-Grip cradles (`RAM-HOL-UN8BU`, `RAM-HOL-UN9U`, and `RAM-HOL-UN11U`) are built differently from phone X-Grips. Tablet X-Grips have a flat four-hole AMPS rear housing with no molded ball stud, meaning you must bolt a `RAM-B-202U` round AMPS ball plate to the back of a tablet X-Grip before it can attach to a socket arm. We cover every model number in our RAM X-Grip overview and sizing guide.
Custom Cradles: RAM Diamond Base (RAM-B-238U) vs. Round AMPS Plate (RAM-B-202U)
Custom device-specific RAM cradles (`RAM-HOL-*`), Garmin spine brackets, and powered GPS docks require a separate aluminum RAM mount adapter plate bolted to the back. Count the screw holes on the rear of your holder to pick the right plate:
1. Two-Hole Pattern Cradles (Use the RAM Diamond Base `RAM-B-238U`): Composite RAM form-fitting cradles for Garmin handhelds, iPads, Spot satellite messengers, and two-way radios have two mounting holes spaced 1.912 inches apart on center. Those holders require the RAM Diamond Base with 1-Inch Ball (`RAM-B-238U`), which measures 2.43 inches by 1.31 inches and matches that exact two-hole spacing.
2. Four-Hole AMPS Pattern Cradles (Use the RAM 2.5-Inch Round Plate `RAM-B-202U`): Dedicated motorcycle and automotive GPS docks (such as Garmin Zumo XT, XT2, and Montana powered cradles or TomTom Rider docks), along with RAM Tab-Tite and tablet X-Grip holders, use the industry-standard four-hole AMPS rectangular hole pattern measuring 1.181 inches by 1.496 inches (30mm by 38mm).
Those cradles pair with the RAM 2.5-Inch Round Plate with AMPS Hole Pattern and 1-Inch Ball (`RAM-B-202U`), which is also pre-drilled with a three-hole 120-degree pattern (`1.812-inch` diameter). Although the diagonal corners of a four-hole AMPS rectangle also sit 1.912 inches apart, bolting all four corners to the round `RAM-B-202U` plate prevents heavy GPS docks and tablet cradles from flexing under vibration. Learn more about hole spacing in our AMPS mounting pattern guide.
Important: Never Use Thread Locker on Composite RAM Cradles. Do not apply Loctite or any anaerobic liquid thread-locking compound to the screws that fasten an aluminum ball adapter plate to a plastic or composite cradle. Anaerobic chemicals attack polycarbonate and ABS plastics over time, causing stress cracks and brittle failure around the screw holes. Hand-tightening the included machine screws into the nylon-insert lock nuts (nylock nuts) provides full vibration resistance without chemical damage.
Assembling a Custom Cradle Step by Step
When you purchase a form-fitting RAM composite cradle, the small hardware bag containing `#8-32` pan-head machine screws and `3/8-inch` hex nylock nuts is packaged inside the cradle box (rather than with the bare aluminum ball plate). Follow these five steps to attach the adapter plate:
- Locate the hexagonal nut slots on the front face of the cradle: Look inside the empty cradle cavity (the side that touches the back of your device). Around each screw hole, you will see a small recessed six-sided pocket shaped to capture the nut so it cannot spin while you turn the screw.
- Press a nylock nut into each hexagonal slot: Orient each nut with its rounded nylon locking ring facing outward toward the front of the cradle (so the screw enters the metal threads first and finishes through the nylon collar), and press the nut firmly into the hex recess until it seats flush.
- Insert the machine screws from the back: Hold your `RAM-B-238U` diamond base or `RAM-B-202U` round plate against the flat rear surface of the cradle, and push the included `#8-32` screws through the adapter plate holes and into the cradle holes.
- Tighten with a hand screwdriver: Hold a fingertip against the nut on the front face
