The ServoCity Set-Screw Shaft Coupler (4mm Round Bore to 5mm Round Bore) facilitates the connection of 4mm diameter shafts to 5mm diameter shafts. It features M5 set-screws at each end to secure the shafts, making it ideal for applications with limited space. The coupler includes built-in shims at both ends, allowing it to operate adjacent to a bearing without contacting the outer race.