SDM® chainrings replace your existing spider and chainring with one clean looking, lightweight, and stiff piece of machined billet. They are available in 3 different offsets: standard 6mm offset, Boost 3mm offset, and BB30 short spindle 0mm offset. Recommendations Recommend the use of a clutch style rear derailleur for the best chain security. An L-wrench works best since the crank spindle may contact a socket adapter and prevent it from engaging properly. Use the same 3 bolts to attach the Wolf Tooth ring or if you need, we carry replacement bolts