It's a stack spacer. It''s a top cap. It''s both! The Wolf Tooth Ultralight stem cap is designed specifically for carbon steerers that require that the steer tube extend above the stem.
- 1 1/8" top (straight 1 1/8" or 1 1/2" to 1 1/8" taper) steerer tubes only
- Light-weight and durable 6061-T6 aluminum