Standard self adhesive backing is 75mm in diameter. Go for standard self adhesive base if you able to remove the old valve without damaging bladder
Large self adhesive backing is 100mm in diameter. The large base will allow you to repare bladders with heavily damaged area around the valve.
1. Peel off by immersing your old valve to boiling water for about 3 to 5 min and gently start peeling off. If it doesn't work then cut the old valve.
2. Wipe area where valve will be sticked with alcohol pad (provided)
3. When the area is dry, peel of the paper backing and place valve on bladder
4. Press valve from center to outward gradually.
5. Heat up the self adhesive backing with hair dryer for better bonding.
Other valves are available, see my other items on ebay.