If you're using half insoles to fill some excess space in your shoe it's best to choose a size down in half insoles. For example, if you're a 39/UK 6 you can use the 37-38 insole. This is because you don't want to make the shoe narrower if the width is fine.

Half rubber insoles available in 35-36, 37-38, 39-40 

These rubber insoles allow the foot to stay cool and dry allowing breathability from the holes.

Made in Italy.  Contains latex.