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This shim will let you easily fit the 27.2mm Dual-Position Seatpost or ShockStop Seatpost into your larger seat tube. Just drop the shim in your frame's seat tube and insert the seatpost. Once installed, the shim is essentially invisible.
• Fits 28.6, 29.8, 30.0, 30.9, 31.6, and 31.8mm outer diameter
• Fits 27.2mm inner diameter
• 100mm (4-inch) length spreads out clamping load along seatpost and frame