Our selection of bottom bracket shells includes threaded, non-threaded, BB30 and PF30 in a variety of sizes and materials. They are machined in one operation. The threads, bores, and faces are as perfectly concentric, square, and parallel as can be manufactured on modern CNC equipment. There is no need for any pre-machining on the framebuilders' part before fabrication. Our threaded bottom bracket shells are 1.37" x 24 threads per inch (also known as British Standard, ISO/English or BSA) or M47 x 1 (also known as T47). They are right and left threaded and compatible with all modern bottom bracket spindles. Our PF30 bottom bracket shells are compatible with PF30 eccentric bottom bracket shells.