This Hyper Coupler has an 8mm round bore on one end and a 6mm D-bore on the other. While it has many uses, one common one is to join the 6mm D-shaft of a motor to an 8mm lead screw. Given the length of the coupler, there’s a considerable amount of surface contact between the outer profile of the 8mm lead screw and the internal bore of the coupler to create a solid connection.
Drawings