Round Polypropylene Plugs - Round Tube Plug - for Cleartec 4" Tubes - Black PP MOCAP PRP4.000BLK (qty10)

I bought these endcaps as part of a "frequently purchased together" offering to fit 4" diameter thinwall clear plastic tubes by the same manufacturer. There was a warning that the caps might not fit tubes from any other manufacturer. THEY DID NOT FIT TUBES BY THEIR OWN MANUFACTURER!!! I have tried several times in the four open ends of two different tubes using several of the ten endcaps. I can not get them to fit into the tubes. My project will not allow me to use any lubricant which might leave a greasy or visible residue or might degrade the plastic tubing over time.I may possibly be able to turn these caps down in a lathe so that I can permanently fit them into the tubes once and done. Maybe not. I can still use the tubes and make my own caps. DO NOT BUY if your purpose involves capping and uncapping the tubes frequently. I think the force you would have to use would split the tubes on insertion or destroy the tubes when you tried to separate them.Too bad because both the tubes and the caps seem very well manufactured, but just not to fit each other.