28.6mm inner diameter for 11/8” for steerers Tapered spacers are designed to go directly above the headset bearing cover or directly under the stem and are relieved internally to save weight, can be flipped over to blend with the stem if preferred Straight spacers are designed to go above a tapered spacer or directly on top of the stem Tapered spacers are 31.6mm outside diameter on top and 34.7mm outside diameter on the bottom