RAM Double Socket Arm - B Size Medium
The arm that's in almost every RAM mount we sell — this is the piece that turns two separate parts into one adjustable mount.
This is RAM's standard "medium" double socket arm in B size (1") — by far the most common combination in RAM's whole catalog, and the piece most of our other RAM base and cradle products assume you already have or are ordering alongside them. It does not come with a base or a cradle: it is the connector in the middle, sold on its own so you can pair it with whichever B-size base and holder your device actually needs.
What's in the bag
In the bag: one two-piece aluminum arm body, the internal spring that pushes the sockets open when loosened, and the stainless-steel knob-and-bolt assembly that clamps it shut. Overall length is 3.73" (94.7 mm) with a socket-to-socket length of 3" (76.2 mm) — RAM's standard reach, long enough to clear a small lip or edge without being bulky.
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 — 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.
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?
All three lengths use the same B-size (1") ball and carry the same weight rating — 2 lbs (0.9 kg) standard use, 1 lb (0.45 kg) heavy-duty use. Length is purely about reach and clearance: go short in a tight cab where you need the device close to the base, go long when you need to clear a dashboard edge, a steering column, or reach around an obstruction.
| Length | Overall length | Socket-to-socket | Weight | Part # |
| Short | 2.42" (61.5 mm) | 1.75" (44.5 mm) | 0.10 kg | RAM-B-201U-A |
| Medium — this product | 3.73" (94.7 mm) | 3" (76.2 mm) | 0.15 kg | RAM-B-201U |
| Long | 6" (152.4 mm) | 5.31" (134.9 mm) | 0.26 kg | RAM-B-201U-C |
Specifications
| Overall length | 3.73" (94.7 mm) |
| Socket-to-socket length | 3" (76.2 mm) |
| Ball size | B Size (1" / 25 mm), both ends |
| Weight capacity, standard use | 2 lbs (0.9 kg) |
| Weight capacity, heavy-duty use | 1 lb (0.45 kg) |
| Materials | Marine-grade aluminum |
| Weight | 0.32 lb (0.145 kg) |
| Packaging | Poly bag |
| Included | Arm body + spring + knob/bolt — no base or cradle |
| Warranty | Lifetime warranty |
Completes a mount with
This is a connector only — on its own it doesn't attach to anything. Pair it with a B-size base and a cradle for your device to complete the mount. Setting up an in-cab position for precision-ag electronics, this exact arm is what connects a base to a holder for devices like an RTK receiver or a keypad. Need the heavier C size instead? A B-size arm will not attach to a C-size ball — see the C-size arms further down this page instead.
- RAM ATV/Side By Side Rail Ball Base (B Size, Zinc) — the matching B-size base
- FJD Trion V4E Pro RTK Receiver
- FJD Bluetooth Keypad (Easy Control)
- RAM Ball Adapter for John Deere (C Size — needs a C-size arm)
- RAM ATV/Side By Side Rail Ball Base (C Size — needs a C-size arm)
Frequently asked questions
What does this arm actually connect?
Two B-size (1") RAM balls — one on a base (mounted to the vehicle) and one on a cradle or holder (gripping your device). The arm is the middle piece that lets you angle and lock the device once both ends are in place.
How do I know if I need the short, medium or long version?
It's purely about physical reach and clearance, not strength — all three lengths in B size carry the same weight rating. Choose short for a tight, close-in mount; medium (this one) for RAM's standard reach; long when you need to clear an obstruction like a dashboard edge or steering column. See the length comparison table further down this page.
Can I adjust the angle after it's mounted?
Yes — that's the whole point of the ball-and-socket design. Loosen the knob, reposition the device to any angle, and lock it firmly by hand again. No re-mounting required.
How is it tightened, and do I need tools?
By hand only, using the built-in knob. RAM doesn't publish a torque spec for this arm because it's designed to be adjustable in the field without a wrench. If it won't hold firmly by hand, that's usually a sign you need a bigger ball size, not a tighter grip.
Does it come with any hardware included?
The arm ships complete in its own bag — the two-piece body, the internal spring, and the stainless-steel knob and bolt that hold it together. You still need to add a base and a cradle separately, since the arm only connects two balls that don't exist on their own.
What's the difference between this and the C-size version?
Only the ball diameter and the resulting weight rating. This B-size arm is rated for 2 lbs (0.9 kg) standard use; the C-size medium arm (RAM-201U) is rated for double that, 4 lbs (1.8 kg), and uses a 1.5" ball instead of a 1" ball. Everything else about how they work is identical.
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.