For those wishing to convert a direct-gas-impingement AR to piston operation, Superlative Arms offers its Retrofit Piston Kit that is designed to keep the action clean of carbon residue and heat. The kit includes a 416 stainless steel, Melonite-treated, 30-position-adjustable gas block and operating rod to fit one of four, standard gas system lengths—pistol, carbine, mid and rifle. Excess gas is bled out of the system through the product’s patented Bleed Off Port at the front of the piston block assembly, which is designed to eliminate gas erosion and carbon build-up—the system can be set to use only the amount of gas necessary to reliably function the rifle. An ion-bonded bolt carrier group and installation tools are included. Price: $289. Contact: Superlative Arms LLC; (727) 849-6880; suparms.com.