For square or rectangular pipes add dimensions of all four sides and divide by 3.14
Use a Combo on the “diamond” or bias for enlarged holes and penetrations where damming could be a problem.
Always fit retrofit joints on the downside of flashing.
INSTALLATION
Cut Combo to pipe size as marked on flashing. If RETROFITTING cut down flashing. Apply silicone to base or GBPRO in demanding application and pull over pipe (wrap around for retrofit and apply clips) Form aluminium surround of base to fit profile and fix at 30mm to 50mm centres through aluminium surround.