California Proposition 65: This product contains a chemical known to the State of California to cause cancer. Reduces brush run-out. Strengthens and sturdies brush shaft for better stability and overall reach. Strong positive engagement with tool holder. Flexible Nylon Stems - Distribute pressure evenly and self centers within the part to create an ideal hone. Consistent Cross Hatch Pattern - Helps to seat piston rings and retains oil for lubrication in a combustion cylinder.