AmmoCounter 

Ammocounter is a US brand that has been innovating the blaster hobby for quite some time!
Their main product is of course the Ammocounter which can count the number of darts that you have fired through your blaster. This helps keep track of how full your magazine is, so you know when to reload! Alternatively, you can also have the Ammocounter count up, so you know how many darts you have shot during a particular game or over the entire day!