This set includes four Lang Cylinder Sleeve Hold Downs, which are specialty nuts used to hold down cylinder sleeves during service procedures. With Lang Cylinder Sleeve Hold Downs, the motor can be turned over with the heads off. Applications for the Lang Cylinder Sleeve Hold Downs include: Harley-Davidson® Big Twin®, Twin Cam®, Sportster® and models with 3/8” studs. The Lang nuts are for a 3/8”- 16 UNC thread, and feature a 3/4” hexagon for easy handling.