Spike's Tactical Mil-Spec, Buffer Spring, Fits AR-15 Rifles, Stainless Finish SLA501S This is the same high quality carbine buffer spring that's found in Spike's Tactical complete rifles and lowers. It's a Mil-Spec 17-7 stainless steel buffer spring that features an electro polish finish to give it a smoother quality look and feel. If you need a replacement buffer spring or just need one to finish a build" look no further.