Have you ever find it difficult to understand the A/F ratio from your bikes? Especially when you have more than 2 bikes and lack of instrument to observe the information you want? This all new protable KOSO Mini 4 A/F ratio will be your final solution! With inner battery to allow you don't have to connect the power supply of the bike so makes it more easier to switch from one bike to another. Of course, you also can connect the power supply and leave it on one bike because the size of the meter is so compact and you could place it in any where you like and easily to get the A/F information you want in anytime when you ride.