Metsuki are offering free pd rulers (whilst stocks last) to all UK residents but one per household.
If you often go on cheap glasses websites, you often need a PD measurement - the problem is, the opticians don't give you them and whilst most people do not stray from the default, it is always good to have an accurate reading.
Randomly came across it, ordered one. Hope it may help someone else. I just hope it is not just paper though.