BTR SMALL BORE 7 LAYER HEAD GASKET - 3.940" BORE - .055" THICKNESS - SOLD INDIVIDUALLY - BTR973010 These small bore, seven layer MLS head gaskets from BTR utilize the same sealing technology found in the ever popular LS9 gasket. This is the perfect choice If you have a 4.8 or 5.3 LS and want to turn the boost all the way up! WILL NOT WORK WITH A TRICK FLOW FAST AS CAST LS1 HEAD. For those and other aftermarket cylinder heads, we recommend BTR22033-2.