"ITEM PROVIDES THE MEANS TO MEASURE THE BUILD DIMENSION TO THE END OF THE MAIN SHAFT,USING A STANDARD DEPTH MICROMETER; SECURE ADAPTER ONTO HOLDER ASSY; PLACE COMPRESSOR HOUSING OVER ADAPTER; POSITION MEASURING ARM ON TOP OF HOUSING INNER FACE; MEASURE BETWEEN TOP OF MEASURING ARM AND MAIN SHAFT; DIM. 14.5""L BY 1.0""W BY 1.8""H; WEIGHT,APPROX. 10 LBS; MATERIAL,STEEL"