Hereby we are giving you the standards of glass pipes which are only produced
and out of which the wicks holders can be done:

pipe diametre wall thickness inner hole diam.

4 mm 0,8 mm 2,4 mm see enclosed sample of wick holder
5 mm 0,8 mm 3,4 mm see enclosed sample of pipe
6 mm 1,5 mm 3,0 mm see enclosed sample of pipe
6 mm 1,0 mm 4,0 mm sample not available

These are the only four possibilities of the size of inner hole and pipe. Anything between is not possible.