Parker Hale RBH.1 3/4 rings

Parker Hale dovetail rings. RBH.1, 3/4 scope tube mount for  17mm and 16MM dovetail mount. Minty condition. I was told they should fit the 16 MM dovetail and when I measure the top widest  I'm a little under 16 MM however going off the numbers they say they are for 17 MM.