BRP's "Frictionless" Chain Glide Blocks are CAD designed and CNC machined using UHMW-PE (Ultra Molecular Weight Polyethylene). Thanks to its extremely low coefficient of friction (0.14), outstanding abrasion resistance, superior impact resistance, and self-lubricating properties, UHMW-PE is ideal for getting you through the gnarly stuff. Outlasting OEM chain guides, while offering a practically frictionless guide and unbelievable protection for your chaing and sprocket. The BRP Glide Block is able to absorb a hit without bending and always return to its original shape. Two-piece design easily replaces the OEM slider and aluminum guard.