Our fast spiral reamers feature a tight spiral that is very aggressive as well as a stop collar that stops the reamer when it has gone all the way through the hole. They are made from hi-tungsten tool steel and have a black and gold coating for maxiumum lubricity. They are designed to enlargen holes in structural steel plates found in truck frames, rail cars, bridges and pressure vessels. This set contains 3/8", 1/2", 5/8", and 3/4" sizes of which the 1/2"-3/4" feature 1/2" reduced shanks with machined flats. Made in the USA by Norseman Drill & Tool.