Trend RBT/1 Routabout Jig 18mm x 1/4\" Shank Large RoutaboutAccess to pipes & cables beneath chipboard floors in seconds. For builders, plumbers & electricians.A 250mm diameter opening can be cut and made good in seconds. Designed for use in new or existing 18mm chipboard or similar floors. Cuts only the thickness of the board. No waste, the pce cut out is used to make good the floor.All you need is a plunge router (750 watts or above).A Unibase may be required for certain makes and models of router.Specification-Shank Diameter=1/4 inchFloor thickness=18 mmAccess hole diameter=250 mmPlease refer to UK Building Regulations Approved Document B and any amendments before using this accessory.