where do i find it

I was recently flooded I still have 2.75 tubes but no couplers , or mounts , semroc is out of them?

Hi Well, there's bad news on the SEMROC front, they are winding down and going out of business. When Carl passed away last year the family tried to carry on but when Bruce got hit with something last fall and it almost killed him they decided to close the doors. They are selling off what they have and are making no more. I'm not sure about that tube size you have listed, 2.75" is kinda odd, you think it might be BT80 tubing? It's like 2.6something".

Totally Tubular will most likely have what your looking for. I scratch build from commercial components and this has me scrambleing to buy nosecones and the list gets shorter every month. Their centering rings list is full of "holes", too

Erockets is now carrying Totally Tubular products:

https://www.erockets.biz/brands/Totally-Tubular.html?sort=featured

hi guys the size is 2.75 or 70mm that is the exact size of my project a1to1 scale of stinger man launched sam .so I went to T.T,s site and they don't have them. well I guess I will be making a lot of dust sanding 3in mounts.

I just read this thread. If you have enough tubing you can cut a 5'' to 5 1/2'' length, subtract the inner circumference( pi x 2.75'' =8.635 ) from the outer circumference (pi x 2.84''=8.9176) = .2826 or roughly just over 1/4(.25)''. Cut that out and test fit, glue a piece of notecard or similar inside allowing the coupler to expand inside your tubing. Be careful not to glue it in! If a slip joint you can sand it a little or wrap with plastic wrap before inserting and allow the glue to set up. Then glue in one end, if slip joint. If you need all your tubing for the airframe you can use something larger in dia. to do the same thing. Say LOC 3''ID/3.1''OD, (pi x 3.1''OD =9.734) - 8.635 = 1.099.(~1-3/32'') All specs from the Semroc and LOC sites BTW.