You searched for "parallel bore"
Sick
Sick Bellows Coupling, 21mm Outside Diameter, 10mm Bore, 29mm Length Coupler
Part: KUP-1010-B
Bellows coupling for precision encoder and sensor shaft connections with minimal backlash.
Sick
Sick Beam Coupling, 21mm Outside Diameter, 6mm Bore, 29mm Length Coupler
Part: KUP-0610-B
Small precision beam coupling for compact machinery and automation.