3M HOSE EXTENSION FOR ON/OFF - ON/OFF PLUS HOSES
 
The Extension Hose intake connection is about 1-1/2 inch diameter with two metal nubs inside at the top or bottom. It plugs into the same diameter wall inlets. Use it for a valve hidden behind a sofa. You can leave it plugged in and not lose any suction. It is also a necessity for any otherwise unreachable areas:
How to Use
Simply plug the Extension Hose into your wall inlet and your hose into the Extension Hose.