It's a 10-32 thread on the Harris and M6x1.0 on the other brands. Great tip I had picked up here a while ago. Much more affordable that the Harris product. You can get it in nylon (BPL-NS) or steel (BPL-ZS). It comes with the 3/16" spacer.PodLock is a great addition to the Harris BiPods, however anyone interested should check out T-Nuts.com and get the same lever lock for $6-$8. Simply confirm the thread required and order on line.