RAM Mounts RAM Locking Knob with 1/4in.-20 Brass Hole for B Size Arms RAM-KNOB3LUThe RAM locking knob, includes a brass 1 4in. 20 thread, for 1in. (B size) socket arms; this allowing you to disengage the screwing of the knob. Once you have set your mount in the location you need, you can lock it in place and feel safe that your mounted device will stay right where you left it. Powder Coated Marine Grade Aluminum