Best to use a plumbing cleaner then pipe cement to assemble. For extra secure grip we recommend that you sand off any lose shavings or burs. We then suggest roughing up the part to be glued at the end of the pipe using an abrasive such as a coarse grain of sand paper
Imperial pipe work is measured by the internal diameter metric pipe is measured by the external diameter. You may get a slight variance on the size of imperial pipe internal diameter but only ever by 1 or 2 mm
Colour sent out is grey not white as shown in this picture.