Tapered cones screw into the top of the tap body, provided the tap body is threaded to the top. Fits old series 1/2in and 3/4in BS1010 flat seats. Complete with 17, 19, 20 and 25mm (11/16in, 3/4in, 13/16in, 1in) flat cutters and 2 tapered cones.
eBay