AquaStar MoFlow 12" Square Main Drain Cover w Frame [Lt Grey] [VGB] (12MF103) cfrfilters A header like this is A header like this is useful because it helps manage the water path through the heater while supporting proper assembly structure and sealing The Waterway 660 3570 notched air control is designed for compatible spa systems that use a 1 inch air control assembly with a 1 5 8 inch hole size and a 2 3 4 inch face diameter The AquaStar MoFlow 12 inch square main drain cover with frame in light gray is designed for compatible VGB drain applications where the complete top assembly needs to be restored as a matched set It is a practical option when the goal is to restore a compatible square drain opening with a coordinated VGB style cover assembly