Leapers, Inc. - UTG Model 4, 6-Position Mil-Spec Stock Assembly w/ Buffer, Buffer Tube, & Spring, Black RBU6BM The Leapers UTG PRO Model 4 MIL-SPEC 6-position collapsible AR-15 stock kit is precision machined to tight tolerances. The aluminum receiver extension provides shooters with six different lengths that allow you adjust your rifle for your body type-helping increase your weapon control" reaction time and accuracy. The high quality buffer tube-to-stock fitment ensures there is minimal wobble so that every time you mount your rifle you get a solid cheek weld. This Leapers stock assembly kit comes complete with a polymer stock" aluminum receiver extension" castle nut" locking plate" action spring and carbine buffer. Pick up a quality armorer's wrench and you will have everything you need to either convert your rifle from a fixed stock or install this collapsible stock on a new build.