Sizes and prices: 25mm and 30mm Bumpa Bits, sold in pack of 8 bits. 25mm bits fit a bantam or a larger bird with a short beak. 30mm suits a hyrbrid or large fowl bird.
 
Measure the distance between the nostril and tip of the beak to get the right size. 
 
All bumpa bits will benefit from warming in a cup of hot water prior to fitting, as they are more prone to snapping when cool - take care when fitting.