RAM ATV/Side By Side Rail Ball Base (C Size)
A rugged base for a rugged cab — the C-size foundation for anything that needs to survive a tractor or ATV cab.
This is the heaviest-duty rail base in RAM's ATV/UTV strap-base family. It clamps onto a roll bar, rail or handlebar and gives you a solid C-size RAM ball to build on — the size RAM itself recommends for equipment that has to survive constant vibration, like a tablet or monitor bolted into a tractor, ATV or UTV cab. It is sold as a base only: you choose the arm and cradle that suit your device (see the compatible accessories below).
What's in the kit
In the box: what makes THIS ball base different from item RAM-B-231Z-2 below is the size of the rubber ball on top — everything else in the kit is identical. Both include a strap clamp adapter with a 6" rubber-lined worm-drive strap (clamp range 1.57"–3.15" / 40–80 mm), plus two zinc-coated U-bolts (one for 0.5"–1" rails, one for 1"–1.25" rails) with rubber end caps and a spacer. The only real difference is the ball on top: this one is C size (1.5"), which is rated for roughly double the weight of the B-size version — 4 lbs (1.8 kg) standard use / 3 lbs (1.4 kg) heavy-duty use, versus 2 lbs / 1 lb on the B-size base.
This base is made of powder-coated, marine-grade aluminum.
How RAM's modular system works
Every RAM product on this page is part of the same modular system used across RAM's entire catalog. Once you understand how it fits together, every other RAM accessory we sell will make sense too.
- A base — clamps, bolts, or straps onto the vehicle (a rail, a roll bar, a dash, a windshield, or a device's own housing).
- An arm — connects two RAM balls together. It can be locked at any angle, so once mounted you can tilt, rotate, and reposition the device freely, then lock it firmly in place by hand.
- A cradle or holder — grips the specific device (tablet, phone, GPS unit, camera).
The ball size determines what it can carry. RAM uses five ball sizes, each rated for a different weight/duty class:
| Ball size | What it's for |
| A Size | Rarely used; costs more to make than B Size but carries less. Reserved for small, low-profile items like security cameras. |
| B Size | RAM's most common size, standard duty. Recommended for phones, GPS units, and light tablets in normal use. |
| C Size — used on this product | Heavy duty. Used for larger tablets, handheld computers/scanners, CB radios, and anything mounted somewhere with a lot of vibration or shock — exactly the case in a tractor, ATV or UTV cab. |
| D / E Size | Reserved for large monitors and specialist/military equipment; rarely needed outside those cases. |
Rule of thumb: if the mount will live somewhere that's frequently jostled, vibrated, or under constant load — an off-road vehicle like a tractor, ATV or UTV — RAM recommends stepping up to the larger ball size (C rather than B) for extra stability, even if a lighter mount would technically hold the device's weight.
No tools required, on purpose. RAM arms are designed to be tightened by hand only — there's no official torque spec, because the ball-and-socket joint is meant to be adjustable in the field without a wrench. If hand-tightening doesn't hold your device firmly, that's usually a sign the ball size is undersized for the device — sizing up solves it, rather than over-tightening.
Aluminum or composite — both are built for the outdoors. RAM mounts are made from marine-grade aluminum or high-strength composite, interchangeably depending on the product; both carry a lifetime warranty and similar weight ratings. Aluminum's powder-coat finish handles rough vibration and shock slightly better; composite skips the paint entirely, so it has nothing to chip and is often preferred in high-corrosion or salt-air environments. Neither choice is worse — it's a trade-off between finish and environment.
Specifications
| Ball size | C Size (1.5" / 38 mm) |
| U-bolt clamp range | 0.5"–1.25" (12.7–31.75 mm) |
| Strap clamp range | 1.57"–3.15" (40–80 mm) |
| Weight capacity, standard use | 4 lbs (1.8 kg) |
| Weight capacity, heavy-duty use | 3 lbs (1.4 kg) |
| Materials | Marine-grade aluminum |
| Weight | 0.56 lb (0.25 kg) |
| Included | Base + 2 U-bolts, strap clamp, caps, spacer — no arm or cradle |
| Warranty | Lifetime warranty |
Frequently asked questions
Does this include an arm and a cradle for my device?
No — this is the base only. It gives you a C-size RAM ball to build on. Add a C-size double socket arm and a cradle for your specific tablet, phone or GPS unit to complete the mount.
What ball size does it use, and why does that matter?
It uses C size (1.5"), RAM's heavy-duty size. In a tractor, ATV or UTV cab your equipment takes constant vibration and shock, and RAM specifically recommends stepping up to C size in that kind of environment for extra stability — even for devices light enough that a B-size mount would technically hold them.
How wide a rail or roll bar does it fit?
The included U-bolts cover 0.5"–1.25" (12.7–31.75 mm) diameter tubing, and the strap clamp covers 1.57"–3.15" (40–80 mm) diameter rails or bars — between the two, most common ATV and UTV roll cage and rail sizes are covered.
Do I need tools to adjust it once it's mounted?
No. Like every RAM arm, the double socket arm you pair this base with tightens by hand — no wrench or torque spec needed. If it won't hold firmly by hand, that's a sign to size up, not tighten harder.
What's the difference between this and RAM-B-231Z-2?
Only the ball size. This base uses RAM's C size (1.5"), rated for roughly double the weight of the B-size (1") ball on RAM-B-231Z-2. The clamp range, U-bolt kit and mounting method are otherwise identical between the two.
Not sure which RAM combination fits your tablet, phone or GPS unit? Contact us and we'll help you put together the right base, arm and cradle.