Rodetal BigBoss boss pipe adaptor fits 110mm uPVC pipes and it is suitable to connect 21.5mm pipe boss. The Boss adaptor offers a quick and easy way to fit a pipe boss, making it great for retrofit applications where limited access prevents using a strap-on boss adaptor. A 25mm hole size is required for the 21.5mm (3/4") pipe. Installation requires solvent weld cementing. Installation Guide: 1. Drill the correct sized hole in the required place using a hole saw. Chamfer the outer edge of the hole to help with inserting the fitting. 2. Clean the outer edge of the hole to help with inserting the fitting. Clean the surface around the hole. Apply suitable adhesive around the hole and the inner face of the fitting. 3. Insert the fitting, using a little force and ensure the correct flow direction. 4. Once fitted, connect the appropriate pipe.