This is the C-size (1.5") sibling of RAM-B-201U above: same medium length category, same ball-and-socket mechanism, but built for RAM's heavy-duty weight class. It's the arm RAM itself recommends stepping up to whenever a mount lives somewhere with constant vibration or shock — a tractor, ATV or UTV cab being the textbook case. Sold as the connector only, no base or cradle included.

What's in the bag

In the bag: the two-piece aluminum arm body with its internal spring, and the knob-and-bolt assembly that clamps both sockets shut. Overall length is 5.69" (144.5 mm) with a 4.66" (118.4 mm) socket-to-socket span — RAM confirms the arm's own weight is already factored into the published weight capacity, so the 4 lbs (1.8 kg) rating is what the arm can carry in addition to itself.

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.

1. A base — clamps, bolts, or straps onto the vehicle (a rail, a roll bar, a dash, a windshield, or a device's own housing).
2. 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.
3. 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:

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.

Inside a double socket arm

A RAM double socket arm is the piece that does the actual adjusting in the system described above. Two cupped "socket" halves clamp around a ball on each end; a single knob and bolt running through the middle squeezes both sockets shut at once. On most double socket arms, a small spring inside pushes the sockets open again as soon as you loosen the knob, so the arm falls open by itself and you don't have to pry it apart to reposition a ball — a detail RAM's own documentation confirms, and one you won't usually see spelled out on a spec sheet.

That spring is also where the arms in this family differ in a way that's easy to miss: RAM's own product documentation notes that the shortest B-size arm (RAM-B-201U-A) does NOT include the pin spring the medium and long arms have — its very short body doesn't leave room for one. In practice this only means you open that particular arm by hand rather than it springing open on its own; it locks and holds exactly the same way once tightened.

The knob itself is a stainless-steel hex bolt with a black finish running through a nylon or composite handle — confirmed on RAM's own documentation for this arm family. If it's ever disassembled, the correct order to rebuild it is: bolt through the hex hole in one socket casting, the second socket casting, then the plastic washer, the metal washer, and finally the knob. Every arm in this family also has a composite sibling (for example RAP-B-201U-A instead of RAM-B-201U-A) that uses high-strength composite instead of marine-grade aluminum — same dimensions and same ball size, just a different material trade-off (see the materials section above).

Which length do you need?

Both lengths use the same C-size (1.5") ball and carry the same weight rating — 4 lbs (1.8 kg) standard use, 3 lbs (1.4 kg) heavy-duty use. RAM also makes a long C-size arm; we currently stock the short and medium lengths, which cover the great majority of tractor, ATV and UTV cab installations. Ask us if you specifically need the long C-size version.

Specifications

Completes a mount with

This is a connector only. Pair it with a C-size base and a cradle for your device to complete the mount. In an in-cab precision-ag setup this is the arm most tablets and rugged handhelds should use — the shock and vibration in a cab is exactly what RAM's own guidance says warrants stepping up from B to C size. Need the lighter B size instead, for example to pair with a phone or a keypad? A C-size arm will not attach to a B-size ball — see the B-size arms on this page instead.

• RAM ATV/Side By Side Rail Ball Base (C Size) — the matching C-size base
• RAM Ball Adapter for John Deere (C Size)
• FJD Bluetooth Keypad (Easy Control) — B size, needs a B-size arm

Frequently asked questions