Valve Stem Seals (16 pack) .530", 8mm R6612-16 AFR6612-16 Suit GM LS1 LS1 VALVE STEM SEALS .530" For over FORTY-FIVE years Air Flow Research has been defining technological leadership in cylinder head manufacturing and flow dynamics. This complete commitment to performance has enabled Air Flow Research's cylinder heads to find themselves on the fastest race cars and the most powerful street machines in the country. As every engine builder will attest to, the secret to increasing horsepower and performance lies in the cylinder head. Air Flow Research's cylinder heads outflow and out horsepower everything in their league.