RAM® Pin-Lock™ 6針安全螺帽（適用D及E尺寸插座臂）

Fits perfectly on my 3.38" arm and the 1/2"-20 threading is solid, so no wobble when I torque it down. The key knob gives me a better grip than the standard knob ever did.

The key knob is a nice upgrade—it makes tightening the arm mount way easier than the stock nuts, and the 1/2"-20 threading fits perfectly on my 3.38" arm. I've used it a few times now and it holds solid with no loosening, even on rough terrain.

Took a bit of effort to thread onto my D-size mount, but once it seated, this nut locks in tight with that 1/2"-20 thread. The key knob makes it easy to adjust, and I love that it replaces the stock knob for added security on my gear.