Wolf Tooth T47 Internal Bottom Bracket. Features: Custom engineered by Wolf Tooth to be durable, reliable, lightweight, and smooth Weather sealing was a main focus with o-ring seals on the spindle and inner shell, a wiper connection seal between the bearing and the end cap, bearing race seals, and labyrinth end cap design To prevent creaking, spindle bushings separate the bearing inner race and crank spindle to eliminate metal-on-metal contact Custom chrome bearings are hardened for durability and reduced friction with ZNA corrosion-resistant coating, while ball diameter, width, and counts were custom selected for performance with each spindle diameter Machined in Minnesota, USA Specs: Model:AlSl 52100 Custom Spindle Interface:24mm Shell:T47 Internal Shell ID:47mm Width:85.5 Color:Black