The Seneca Woodworking Imperial Thickness Gauge for the Domino DF500 allows you to quickly and effortlessly adjust the Domino fence offset to center your mortise on a variety of imperial material thicknesses. The gauge installs in less than a minute using a Torx T10 bit (not included), and is a direct replacement for the metric thickness gauge included with your Domino DF500. The Imperial Thickness Gauge is designed to center on 1/2", 5/8", 3/4", 7/8", 1", and 1-1/8" nominal ply thicknesses. We currently offer two products to create the correct offset for mortising imperial lumber; The Domiplate and the Imperial Thickness Gauge. If you primarily work in only 1/2 and 3/4" material, The Domiplate is probably the right choice because it provides a reliable way to set a specific offset and create many mortises with absolutely no possibility of "Fence drift". On the other hand, If you frequently use material other than 1/2" and 3/4", the new thickness gauge allows you more versatility in choosing different fence offsets. However, it doesn't provide that extra "insurance" against fence drift that the Domiplate offers.