This is a foundation component: a 2.5″ round aluminum plate with the industry-standard 4-hole AMPS pattern, topped with RAM's most common ball size — B Size. Bolt it directly to a flat surface as a drill-down base, or use it as an adapter that lets any AMPS-pattern device holder connect to a B Size RAM double-socket arm.

Features

• 2.5″ round plate connects to RAM device holders containing the universal AMPS hole pattern
• Included B Size 1″ RAM rubber ball allows connection to any B Size RAM double-socket arm; ball-and-socket technology allows near-infinite adjustability
• Made of powder-coated, marine-grade aluminum for durability and reliability in the most demanding environments
• Also carries a 1.912″ two-hole spacing that lines up with RAM's diamond ball base pattern — useful if you're standardizing hardware across a fleet that mixes round and diamond bases
• Backed by a lifetime warranty

How RAM's modular system works

Every RAM mount is built from up to three parts that click together, and the same parts mix and match across RAM's entire catalog:

• 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 locks at any angle, so once mounted you can tilt, rotate, and reposition the device freely, then lock it firmly by hand.
• A cradle or holder — grips the specific device (tablet, phone, GPS unit, camera).

Not every product includes all three parts — some are just the base, some bundle a cradle, some are a complete kit. Further down this page we say plainly which parts this specific product includes, so you know exactly what you're getting and what, if anything, you'd need to add.

The ball size determines what it can carry. RAM uses five ball sizes, each rated for a different weight and duty class:

• A Size — rarely used; costs more to make than B Size but carries less. Reserved for small, low-profile items like security cameras where bulk matters more than capacity.
• B Size (1″ ball) — RAM's most common size, standard duty. This is what RAM recommends for phones, GPS units, and light tablets in normal use.
• C Size (1.5″ ball) — heavy duty. Used for larger tablets, handheld computers/scanners, CB radios, and anything mounted somewhere that gets a lot of vibration or shock — exactly the case in a tractor, ATV, or UTV cab.
• D and E Size — reserved for large monitors and specialist/military equipment; rarely needed outside those cases.

This product uses a B Size ball (1″ / 25 mm) — RAM's most common size, and the one RAM recommends for phones, GPS units, and light tablets in normal use. If what you're mounting is larger or will live somewhere that gets constant vibration — a tractor, ATV, or UTV cab — our C Size version (RAM-202U) is the sturdier match.

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 for extra stability, even if a lighter mount would technically hold the device's weight.

Round plate or diamond plate? This plate is 2.5″ round with a 4-hole AMPS pattern (1.181″ × 1.496″), giving it the widest compatibility with RAM and third-party cradles. It also happens to include RAM's 1.912″ two-hole spacing, the same spacing used on RAM's diamond ball base (see our RAM-B-238U) — so in a pinch, a cradle drilled for the diamond pattern can also mount to this plate. If you don't need that flexibility and want the smallest, lightest possible base, the diamond plate on its own is the better choice.

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 part; 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

Frequently asked questions

What does this base actually attach to?
You bolt the round plate directly to a flat surface (a dash, a bracket, a device panel) using the holes in the plate, or you attach it as an adapter to a device or holder that already has a matching AMPS hole pattern on its back.

Does it include an arm or a device holder?
No — this is the base plate and ball only. Pair it with a B Size RAM double-socket arm and an AMPS-compatible cradle (for a phone, GPS unit, or light tablet) to complete the mount. Ask us and we'll match the right combination to your device.

Is there a backing plate for mounting through thin plastic?
Yes — RAM also sells a version of this base with an integrated backing plate (RAM-B-202-225-2U) for extra support when the mounting surface is thin plastic. Ask us if that's a better fit for your surface.

Do I need B Size or would C Size be better?
For a phone, GPS unit, or light tablet in normal use, this B Size version is exactly what RAM recommends. If you're mounting a larger tablet or handheld computer in a tractor, ATV, or UTV cab that takes real vibration, step up to our C Size plate (RAM-202U) instead.

Is drilling required?
Yes — this base is meant to be bolted or screwed down, either directly to a flat surface or to a matching AMPS device holder. Common screw sizes are #8, #10, M4, or M5; if you're pairing it with a RAM holder, the holder ships with the hardware it needs.

Does this share a hole pattern with the diamond ball base?
Yes — in addition to its own 4-hole AMPS pattern, this round plate has a 1.912″ two-hole spacing that matches RAM's diamond ball base, so a diamond-pattern cradle can also be bolted to it.