RAM ATV/Side By Side Double Ball Rail Mount with Diamond (AMPS) Base
The universal foundation — base, arm and an industry-standard AMPS plate that opens the door to thousands of third-party and RAM cradles.
This is the building-block version of items RAM-B-149Z-2-GA41U and RAM-B-149Z-2-202AU below: same strap-and-U-bolt rail base and double socket arm, but instead of a device-specific cradle it ends in a diamond-shaped adapter plate drilled to the industry-standard AMPS hole pattern. That single detail is what makes it so versatile — the AMPS pattern is used across a huge range of RAM's own cradles (tablets, radios, scanners) and third-party mounting hardware, so this base becomes the starting point for almost any device you need to add later.
What's in the kit
In the box: strap clamp adapter, two U-bolts (0.5"–1.25" rails), a B-size medium double socket arm (3" socket-to-socket), and the diamond adapter plate itself — a 2.43" x 1.31" (61.7 x 33.3 mm) plate with a 2-hole AMPS pattern (1.912" / 48.6 mm hole spacing). The plate is what you bolt your own AMPS-compatible cradle to; it does not include a cradle.
Made of powder-coated 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) |
| Arm length | Medium, 3" socket-to-socket (76 mm) |
| Adapter plate hole pattern | 2-Hole AMPS, 1.912" (48.6 mm) spacing |
| Adapter plate size | 2.43" x 1.31" (61.7 x 33.3 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 + arm + AMPS diamond plate — no cradle included |
| Warranty | Lifetime warranty |
Frequently asked questions
What can I actually attach to the diamond plate?
Anything drilled to the industry-standard 2-hole AMPS pattern (1.912" hole spacing) — that covers a large share of RAM's own tablet, phone and radio cradles, as well as many third-party mounts. It is not specific to any one device.
How is this different from RAM-B-149Z-2-GA41U or RAM-B-149Z-2-202AU?
Same rail base and arm on all three. This one ends in a universal AMPS plate so you choose your own cradle later; the GA41U version ends in a Garmin-specific form-fit cradle already installed, and the 202AU version ends in a round camera stud plate instead of an AMPS plate.
Does a cradle come included?
No. This product is the base, arm and AMPS adapter plate only — you add whichever AMPS-compatible cradle matches your device.
What ball size does the arm use?
B Size (1"), RAM's standard duty size, matched to the medium double socket arm included in this kit.
How wide a rail does the base clamp onto?
U-bolts for 0.5"–1.25" (12.7–31.75 mm) diameter tubing, and the strap clamp for 1.57"–3.15" (40–80 mm) diameter rails or bars.
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.