These mount onto the front side of bass drums and are used to anchor the drum, and decrease sliding forward when being played Mounts with 4 holes in a dianond pattern. A very similar type spur is used on Gretsch, GMS and Ludwig among other pro drum companies. This model does have a specific left side and right side spur and does have notched closed / open lock angles. In addition to use on standard sizes bass drums, we also recommend this model for smaller 16 and 18 inch kick drums, as it has an nice extended leg reach. The hole spacing for these spurs is as follows: The two holes spaced horizontally accross from each other are spaced 1 3/4in apart. The vertical holes are 2 7/16" apart. This is a 2 position spur, 1 open and 1 closed position. Compares to SC-BS4 SP-60 SP-39 BDS-1CR BDS-6CR G9013 GS-BDS4
