0.9 mm

It was meant to be 1 mm, but I couldn’t be fagged to adjust the Vernier callipers and take the shots again - it took me two goes anyway!

Correction - on closer inspection this should be titled 0.95 mm
 
Playing with the cheap and cheerful extension rings again, and I thought I would make a little more of the shot.
 
Spent much of the morning playing with monochrome and the EOS R, and Tesco delivery this afternoon
 
Many thanks to  Osuzanna  for hosting Tiny Tuesday this month.