Tapered adapters are designed to CONNECT and DISCONNECT from your equipment quickly.
The inside of the large end of the adapter is tapered and fits perfectly onto the matching taper of dust gates, universal hoods, jointer hoods, saw hoods and floor sweeps.
The small end is 2-1/2” outside which fits 2-1/2” hose and the 2-1/2” coupler. The inside diameter of the small end is 2-1/4”. The popular 2-1/4” shop vacuum hose fits in the end perfectly. In other words, this fitting allows you to connect a shop vacuum to a machine that has a tapered 4” outlet. This usually is not the best situation because those machines come with a 4” outlet intended for a dust collector with a 4” inlet. But when all you have is a shop vacuum, you’ve got to do what you’ve go to do and this fitting will allow it.