With this tool you can easily adjust solid lifters on an Esslinger BB7, RSI, XT, TST, EST, ST, ARCA or late model SVO head! Comes pre-modified to allow the use of a 5/8" wrench on the adjuster stud while being able to torque down the 13/16" jam nut with the crows foot tool. Not for use on 14mm studs, only for the "Jumbo" 5/8" studs we use on these higher performance heads!