T/Y Corrugated Coupler, Connects to 3-in. and 4-in. Pipe

I thought it was a bit expensive, but it is the only way that I could find to join two 4 inch drains into a single outlet. It is flexible and fits the 4" corrugated drain hoses perfectly, although the user should be prepared to tape the joints if water leaking is any kind of issue. Gorilla makes a special rubbery black duct tape that is a couple of dollars more than their very good black duct tape, and it prevents leaks at the joint.

Circumference isn’t exact but flexible enough to make it work

It does the job. The flex part of the T/Y fitting is detachable as well.

All good

It doesn't fit any 4" pipe . Don't buy them supper cheaply made and had to go buy the real 4" corrugated fittings to complete my drainage project.

It worked fine for the job

Used this to connect two downspouts to one drainage pipe. solid construction, flexible neck, I expect this will last quite a long time as long as it's not exposed to extreme weather.

Does the job if it’s close to the surface - but the plastic is super thin and cheap. If it was under a half a foot of soil gravel it would surely collapse.