Hydro-Bats are designed to fit on standard wheel heads with bat pins placed 10" (25.4 cm) apart. Each bat is made of super strong Hydro-Stone instead of standard pottery plaster and features durable hard rubber grommets that have been cast into the underside so you can be assured of a snug wheel head fit. This smaller size bat requires Hydro-Bats' 6" to 10" adaptor