Bonus and different foods.
Why blue and yellow ?
Bonus comes in two colours blue and yellow these both being visible to your dog this adds another level to training.
Your dog being able to see the reward , knowing its there and working for it.
Foods
The lid Bonus comes with can be changed depending on what you want to reward your dog with .
Thinner foods such as natural yoghurt , pureed fruit and veg , dog pate this will fit through the existing lid and hole.
For slightly thicker foods dog pate mashed fish you can pop out the silicone one way valve making a bigger hole to dispense through , although the silicone cannot be put back on . 
For thick foods such as the thicker Pates and Raw food the lid can be removed ( screw cap ) creating a larger hole allowing you to squeeze silicone to dispense amount to your dog screwing lid back on when you are finished.
Please contact your local vet if you are unsure over what foods are safe for your dog and how much .