4 tap guides 100% USA-made, Lifetime Warranty & Innovative Award-Winning Tools The "v-groove" on bottom allows use on round & cornered materials. Ground base allows for use on flat materials Heat-treated steel: tight tolerance & stronger tool to clamp Use on wood, metal, plastic & more. Tap sizes are embedded on top of drill bit guide or tap guide for explanatory sizes. Big Gator Tap Set is a 4 piece set of 4 tap guides. The tap guides start every hole straight and helps prevent tap breakage! All the guides have a "v-groove" on the bottom to allow you to work on corners or round surfaces. All guides have a ground base to be used on flat surfaces. Each guide is heat-treated for durability, allowing a tight tolerance. The guides work great on corners, round and flat surfaces.100% American-made quality and a Lifetime Warranty on every guide! Set includes one Standard V-TapGuide, one Metric V-TapGuide, one STI-UNC V-TapGuide (coarse threads), and one STI-UNF V-TapGuide (fine threads). A V-TapGuide is a tap guide that answers the call to accurately guide hand tapped threads on the inside of a hole to accept a machine screw or bolt. If you start every hole straight, it will help prevent tap breakage and increase the tap life. The tap guide is easy to use: place the tap guide on the work surface, with the "v-groove" side resting on the surface. Insert the tap through the guide into the pre-drilled hole and turn it clockwise. The tap will then be aligning perpendicularly using the guide as the base; this will ensure a straight and accurately tapped hole. Every few turns, back the tap out counter-clockwise to clear the chips. Lifetime Warranty on all tap guides. Tap Straight - Every Time!