These parts are machined out of 2.5" x 2.5" x .5" 6061 T6 aluminum extrude. The pocket is .350" deep and it is cut in two .175" deep passes using a 3/8" end mill. The window is cut with a .25" end mill then finished with a 3/32" corner rounding mill. After milling, the parts are faced on a 150 grit belt sander. It takes about 45 minutes on the machine to make one of these parts, and that includes tool changes, and turning the part over. Milling three at a time shaves about 10 minutes off.