This is a good quality coupling set for a variety or worm gearbox motors in a similar style to the MCP (Motion Control Products). This is a universal size and can replace most couplings from similar manufacturers of gearboxes.
They are designed to take the shock loading from the motor to the gearbox and are of a good quality.
You can use these to replace the cheap nylon ones or just have a spare set handy. They don't break often (and from all the worm gearboxes we've sold, not a single one has ever failed)
The only ones I've seen break are the nylon ones which can get stripped easily under heavy loads.
They are made to slip over an 8mm D-Cut shaft and are made of a alloy cast type metal.
These will fit (and replace) the Nylon one in the G180-12 Worm drive motor that we sell.
Please note that this coupling set is for the worm drive motor and gearbox we sell.