RAM ATV/Side By Side Rail Ball Base (B Size, Zinc)
The everyday version of our C-size base above — same clamp kit, RAM's standard B-size ball.
This is the direct B-size sibling of RAM-231Z-2U above. It uses the exact same strap-and-U-bolt clamp kit, but carries RAM's standard-duty B-size ball instead of the heavy-duty C size — RAM's own recommendation for phones, GPS units and light tablets in normal use. Like the C-size base, it is sold base only: pair it with a B-size double socket arm and a cradle for your device.
What's in the kit
In the box: 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 — identical hardware to the C-size base above. The verified difference between the two products is the ball itself: this one is B size (1"), rated 2 lbs (0.9 kg) standard use / 1 lb (0.45 kg) heavy-duty use, about half the C-size base's rating.
This base is made of marine-grade aluminum and high-strength composite.
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 — used on this product | RAM's most common size, standard duty. Recommended for phones, GPS units, and light tablets in normal use. |
| C Size | 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 | B Size (1" / 25 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 | 2 lbs (0.9 kg) |
| Weight capacity, heavy-duty use | 1 lb (0.45 kg) |
| Materials | Marine-grade aluminum, high-strength composite |
| 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, exactly like the C-size version above. Add a B-size double socket arm and a cradle for your phone, GPS unit or light tablet to complete the mount.
What's the real difference between this and RAM-231Z-2U?
Only the ball on top. The clamp kit, clamp ranges and mounting method are identical between the two products — the difference is that this one carries a B-size (1") ball rated for lighter loads, while RAM-231Z-2U carries a C-size (1.5") ball rated for roughly double the weight.
Is B size strong enough for a tractor or ATV cab?
For a phone or a light GPS unit, yes — B size is RAM's standard recommendation for those devices. But for anything heavier, or if the mounting location gets unusually rough vibration, RAM recommends sizing up to C size (see RAM-231Z-2U) rather than pushing a B-size mount past its rating.
How wide a rail does it clamp onto?
The same range as the C-size base: U-bolts for 0.5"–1.25" (12.7–31.75 mm) tubing, and the strap clamp for 1.57"–3.15" (40–80 mm) diameter rails or bars.
Do I need tools to tighten it?
No. The double socket arm you pair it with locks by hand, no wrench or torque spec required — the whole point of the ball-and-socket design is field adjustability without tools.
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.