SWB’s the original  aluminum Double-Loc Servo Arm. User holes are 4) 1/16" thru holes for those that need to tap for 2/56 or 2mm. Hole spacing is .15

These arms are not only designed to clamp around the output shaft, but they also make up for any inconsistencies in the output shaft sizes. Half arms are measured from the servo screw hole to the outside hole.