CT-494 Igniter Erosion Gauge The CT-494 accurately determines wear on 10 of our most popular surface gap igniters, insuring maximum igniter life without exceeding safe wear limitations. For use with the following igniters: CH31547, CH31621, CH34055, CH34168, CH34187, CH34269, CH34304, CH34406, FHE146-7 and FHE246-4. Heavy duty protective sleeve included. Shipping weight: 1 oz./.28g.