Currently the only Bi-Pod that I own is the old "L" series Harris Bipod, 9-13" Benchrest model--- ...yeah I know, the 9-13 isn't technically the benchrest model according to Harris (there is one just a tad shorter---however I am 6'3", so it IS for me, LOL.) but that is what mine measures from the bottom of the stock to the bottom of one leg extended=12 inches, and my original package says that it is a "L" series---I prefer that exact length. ANYWAY, I am in need (more of a want to be honest) of another (spare, HA, there we go!) Bi-Pod. I KNOW I want a swivel model (duh) for leveling on uneven terrain, and I like Harris' LM or BRM with their leg notches. I don't quite understand what the Harris "M" models are except I assume that they are "manual lock"? If manual lock is like my old L series, I like mine! Does anyone want to take a stab at this and help me out please??? Sad to say, but, I don't understand Harris' new descriptions.