Compatible with multiple frame sizes: adjustable length with spacers to fit thru axle hubs of 135, 142, and 148 mm, and bike frames up to 176 mm wide, enabling use across a range of bike models. Secure mounting: tapered heads on both ends fit most trainer mounting holes securely, providing a reliable connection during training with no slippage. material construction: crafted from 6061 aluminum alloy for strength and durability under rigorous use. Frame protection: MTB Road Bike Thru Axle Spacers match the shape of frame dropouts, helping protect your bike frame from potential damage during intense workouts. Practical use scenario 1: You own multiple bikes (road and MTB) and need a single trainer axle that supports 135, 142, and 148 mm hubs while fitting frames up to 176 mm wide. Practical use scenario 2: You perform torque interval sessions on a trainer and require a secure, wobble connection to prevent slippage. Practical use scenario 3: You push intense workouts where frame dropout protection helps minimize risk of dropout edge contact and frame damage.