Get a good quality 5/8 inch tube bender. it will bend 316 stainless steel 16mm o/d tubing. use Monsoon EVO2 5/8 fittings
thats what I used in my build
for your information you cannot bend tubing after it as been Crome plated as it will flake off the tubing
also because the tubing as to be polished before and after plating the O/D tolerances may change