This part of GB/T 16709 specifies the assembly dimensions of vacuum pipeline fittings (elbows, T-shaped tubes, cross tubes) of the R5 series, with nominal diameters ranging from 10 mm to 250 mm, non-bake type and non-knife-edge flanges.
GB/T 16709.1-2010 Referenced Document
GB/T 4982 Vacuum technology--Quick release couplings--Dimensions--Part 1:Clamped type