Flame-retardant filters are engineered specially for use on the No-Toil Super Flo Kit. Flame-retardant filters, or FRF’s, are made of the highest quality dual-stage foam and bonded with the best glues available. The inner foam is flame-retardant and is self extinguishing foam. Since the Super Flo Kits come with a filter cage with the backfire screen removed, the flame-retardant foam of the FRF protects you against the possibility of backfire sparks igniting your filter on fire. Hand made in California, FRF’s come with a one-year warranty.