The Pro-Graad Aluminum Reducing Bushing Adapter is a 4pc telescoping wheel adapter nested set for 1/2" wide bench grinding or abrasive wheels with a 1-1/4" or 1" arbor hole. Adapter will reduce a 1/2" wide wheel with a 1-1/4" or 1" arbor hole to 1/2", 5/8" and 3/4" diameter shaft sizes The 4 piece set includes the following sizes: #1: ID 1/2" x OD 5/8" x H 1/2"; #2: ID 5/8" x OD 3/4" x H 1/2"; #3: ID 3/4" x OD 1" x H 1/2"; #4: ID 1" x OD 1 1/4" x H 1/2". Adapter is precision machined from aluminum to ensure wheel runs balanced and without vibration. The adapter will not deform or degrade like plastic wheel adapters.