This is a small selection of the sizes available. I have the sizes mentioned in the ARRL Antenna Handbook. 1/4 inch, 3/8 inch, 1/2 inch, 5/8 inch, 3/4 inch, 7/8 inch, 1 inch, 1 1/8 inch with a wall thickness of 1.42 mm ;0.056 inch, the thickest wall tube available.
Metric sizes start at 10 mm and go to 100 mm.
The metric telescopic range starts at 32 mm and goes to 68 mm. Sizes are 32 mm, 35.6 mm, 40 mm, 44 mm, 48 mm in 1.6 mm wall. 40 mm, 45 mm, 50 mm, 55 mm, 60 mm in 2 mm wall. 61 mm in 2.5 mm wall; 68 mm in 3.25 mm wall