What it connects to

Harnesses: vac-u-lock harnesses hold the toy on a plug mounted in the harness front — sturdier than an O-ring for heavy toys, because the toy cannot lever against a ring, and swapping toys takes seconds.

Handles and grips: a vac-u-lock handle turns any compatible toy into a toy with a proper grip — a genuine accessibility win if reach, wrist strength or angle is the limiting factor.

Machines: most consumer sex machines ship with vac-u-lock adapters as the standard fitting. If machine use is on your horizon, buying vac-u-lock compatible toys now is the future-proof choice.

What the hole is — and isn’t

It is a mounting socket, full stop. It is not a suction cup (it will not stick to a wall on its own — though an accessory suction base can add that), and it is not a flare. Whether a vac-u-lock toy is anal-safe still depends on the base being wide enough to stop travel; check the base spec, not the hole.

The cavity does add one cleaning duty: water gets in, so rinse the hole properly and let it drain and dry before the toy goes back in the drawer. A cotton bud reaches the bottom if you are thorough. On our shelf the hole is a maker option, and currently it comes from one maker’s catalogue, so the compatible list below is large but not universal.

Fit and grip tips

The grip should be snug — working the toy onto the plug with a slight twist seats it fully, and a properly seated toy should not wobble. If the fit is loose (tolerances vary between accessory brands), a wrap of the plug in cling film or a purpose-made sleeve tightens it. Softer pours grip plugs slightly better than very firm ones; very firm pours can need a determined push to seat.