Rankin Industries SP4 Trigger Group
The AR-15 SP4 Trigger Group. SP4 is a hybrid DLC type coating that is the hardest, slickest, and most flexible coating on the market. It makes for a super nice trigger pull. Silky smooth with no grit at all. The trigger group is made of stainless steel and undergoes a special polishing process prior to getting the SP4 coating applied in an extreme vacuum. This is the latest and greatest coating for trigger groups and bolt carrier groups.