Machined entirely from 440C stainless steel and guaranteed for life. Maxhit BB bearings include proprietary double-lip labyrinth seals and extra high pressure Enduro grease to ensure a lifetime of trouble-free, heavy duty performance. Bearings are designed to press directly into your bicycles bottom bracket shell, eliminating the need for the aluminum cups that are traditionally used to carry the bearings. This unique design frees-up space for much larger balls that more than double the load capacity compared to standard BB bearings. The kit includes a full selection seals and spacers to ensure proper installation in any T47 threaded bike.