5/16-18 to 5/16-24 X 1-11/16" long. Zinc plated studs with chrome plated nuts. Mounts exhaust to cylinder heads. Note: Exhaust studs as used in the M8 engine (OEM 10900015) are of a slightly different design, with a small protruding hex-shaped outer-end to aid initial stud-installation, but these early Evo/Twin Cam style studs will still fit. OEM reference 16715-83 (studs), 7593 (nuts)