The Dunham Chuck Stop eliminates the need for unsafe use of parallels or spacers that can cause a hazard for operators and equipment. Provides faster set ups and repeatable results for multi-part applications. Each Chuck Stop has a 1/2" diameter center hole to allow some clearance for drilling or other operations. This can avoid having the drill damage the chuck stop. The jaw gap has been left large enough to accept 1-1/2" width jaws. Each Chuck Stop is made of Durable E-coated Aluminum for longer life, and can be used with workpiece diameter range of 1-1/8" to 5-1/2". The 3 powerful magnets will hold your light weight Chuck Stop firmly in place against the chuck face. Available individually or in 3 and 5 piece sets.