My dust collector system has a 4 inch hose and a 2 inch end on the saw (dust connector). So I needed this quick disconnect to attach the two different size hoses together. It works very well for my needs

I tried to use this thing to connect to the 4" output of my delta jointer and planer, but it just doesn't fit that great... I don't know if I'm just dumb or what, but I was under the impression that it should attach to any machine with a 4" dust port. It didn't fit my machines...

These have a really, really basic problem - they fall off. Another reviewer mentions using duct tape to hold them on - which completely flies in the face of their purpose - to quickly move the hose from machine to machine. The plastic is too hard and the taper isn't designed properly. Manufacturing quality isn't great - they are only more-or-less round and given the taper problems and hard plastic, the results aren't good: They don't slide on most machines' dust outlets deeply enough, they don't seat, and they don't fully seal. I went back to using the raw hose end, which works fine when using a soft hose.

I've used it using a 4" hose to connect it to different machines. For the most part it works well but for some machines it will just get disconnected (no matter how hard you press it). I've found that using duct tape or masking tape around the machine's port helps to keep this adaptor from falling.

I found it a little difficult to get it to thread on my 4" pipe and it didn't seem like it would stay put without a spring clamp. Serves it's purpose though.