For an AR-10 chambered in .308/7.62 with a collapsible stock, if it has an AR-15 carbine buffer tube (which is 7” long on the inside) then it needs a 2.5” buffer and we recommend the KynSHOT AR10 2.5” carbine hydraulic buffer “Shorty” (Part# RB5004) and an AR-10 carbine buffer spring, either the JP 308 carbine buffer spring (part# JPS-OSC-308) or the SPRINCO AR-10 carbine buffer spring (color code ORANGE - Part# SPRINCO-25762).