Ultra Compact 
"Ultra Compact"
HSM motors allow cables, hoses, rotating shafts, etc. to pass through the servomotor’s own shaft. This provides a far cheaper and simpler overall solution with fewer components, leading to a more reliable system. It also gives a more compact servo solution with stiffer regulation. The HSM motor is ideally suited for direct drive. It has a high-resolution feedback system and a large bore (up to 40mm), allowing ballscrews to pass through the shaft.