Transmission mount shims are useful for tuning drive train and drive shaft angles. These shims are 1-1/4″ x 2-3/4″ in size, 1/8″ thick, and made from aluminum. This set of 4 individual shims allow adjustments from 1/8″ to 1/2″. These shims are designed to work with the late model gm style single centered stud mounts, or the early model gm style dual stud mount with 1-1/2″ between hole centers. The base dimensions of 1-1/4″ x 2-3/4″ provide a solid contact between the transmission mount and the transmission crossmember. Attempts to use a standard flat washer as a shim will never provide the same contact or rigidity which these precision shims accomplish. Note: check your transmission mount to assure it has the same pattern dimensions prior to purchasing.