Designed to fit phones with screen size 3.7" - 4.3".  These include the larger smartphones released in 2011 and sooner.  Features an adjustable velcro strap for easy adjustment and comfort.  Made of stretchable, sweat resistant neoprene material and includes reflective markers for safety during night sports activity.  Lightweight design includes a storage pouch for money or other essentials.  Clear plastic cover enables operation of phone's screen, while in the armband pouch.  Cutouts and slit for audio jack on top and bottom.

Even works with some cases and skins.  Tested to work with an iPhone 4 with Otterbox!

Fits many models including:

Apple iPhone: 3G 3GS 4 4s
Apple iPod Nano
Blackberry: Tour, Storm, Bold, Storm 2, Curve
Casio: Exilim, G'zOne Brigade, G'zOne Ravine
Dell: Aero
HTC: HD Mini, Pure, Touch Diamond, Touch Pro, Wildfire, Legend, HD2, Hero, Droid Eris
Kyocera: E3500, E4600, G2GO M2000, Laylo M1400, Loft S2300, Mako S4000, Neo E1100, Tempo E2000, TNT S2400, Tomo S2410, Torino S2300, X-tc M2000
LG: Accolade, Andante, Arena, Bali, Banter, Bliss, Brio, Chocolate, Cookie, Corona, Cosmos, Dare, Decoy, dLite, Encore, enV, Etna, EVE, eXpo, Flare, Fusic, Glance, Glimmer, Incite, InTouch Lady, InTouch Max, Invision, Lillipop, Lotus, Lotus Elite, Lyric, Mini, Monaco, Muziq, Mystique, Neon, Octane, Optimus, Optimus 7, Optimus U, Papaya, Plum, Prada, Prime, Pure, Quantum, Remarq, Renoir, Rhythm, Rumor, Rumor 2, Rumor Touch, Saffron, Samba, Scarlet, Scoop, Secret, Sentio, Shine, Shine Touch, Surf 4GB, Swift, Town, Trax, Tribe, Tritan, Vantage, Venus, Viewty, Voyager, Wave, Wine II, Xenon
Magellan Explorist: GC, 510, 610, 710
Motorola: Adventure, Aura, Backflip, Citrus, Clutch, Crush, Debut, Entice, Evoke, Grasp, Hint, i1, 1290, 1576, 1776, Karma, Moto, Quantico, Rambler, Rapture, Renegade, Rival, Stature i9, Tundra, Droid, Cliq, Devour, Droid X, Droid 2, Droid Razr, Droid Razr Maxx, Cliq XT
Nokia: 2705 Shade, 2720, 2730, 3711, 5130 Xpress, 5230, 5230 Nuron, 5530 Xpress, 5800 Xpress, 6350, 6750 Mural, 6790 Surge, 7020, 7705 Twist, C3, C6, E5, E63, E71, E71x, E72, E73 Mode, N71 Mini, N8, N900, N97 Mini, X3, X6
Pantech: Breeze, Breeze II, Ease, Impact, Link, Matrix, Matrix Pro, Pursuit, Reveal, Slate
Samsung: Access, Ace, Alias 2, Champ, Continuum, Convoy, Gravity 3, Gusto, Highlight, Instinct, Instinct HD, Instinct2, Monte, Smooth, Solid Extreme, Solstice, Strive, Transform, Wave, Zeal, Mesmerize, Showcase
Sanyo: Incognito, Innuendo, Juno, Katana, M1, Mirro, Pro 200, Pro 700, Reclaim, Restore, S1, Vero, Zio, Zio M6000
Sony Ericsson: Aino, Aspen, Cedar, Equinox, Naite, Satio, Vivaz, W518A, Xperia Pureness, Xperia X2a, Xperia X8
Vodaphone 845
HTC: Droid Incredible, Evo, Aria, Desire, HD7, Surround, Eris, Wildfire, Legend, HD2, Hero
LG: Ally, Fathom, Vortex, Vu
Motorola Droid, Droid 2, Cliq, Droid XT, Devour
Sony Ericsson: Xperia X10
Samsung Vibrant, Captivate, Intercept, Behold II, Omnia II, Mythic, Moment, Reality, Craft, Galaxy S, Epic 4G, Fascinate,

Not compatible with Motorola Droid X