My system has a sediment filter, RO membrane and a Charcoal filter. The RO membrane housing has three connections on top. I've purchased the
tfm-16-c membrane which I was told was the replacement part for my system. This membrane has one connection on each end. I was told to put the replacement part (tfm-16-c) into the housing. The original Culligan membrane was slipped on to a hard plastic tube which is attached to one of the three connections built into the housing cap.

When I tried to slip the new replacement part on to the tube , it went in and stopped after 3''. There's a circuliar ridge at thsat point. Yet the original membrane passed right through.

I would appreciate the help in knowing how I can make this "Culligan compatible membrane" work.

I do have a photo of my system if that would help. Thanks Rob