The Blackhawk Driveline Breather Kit helps to prevent water and mud from entering sensitive parts of your driveline. Why do I need aftermarket (diff) breathers? Factory fitted breathers are often only at the top of your diff, or at best mounted inside the vehicles chassis rails. It's all too common to have these parts exposed to water when heading off road. Additionally the factory breathers are often only a tube with a plastic cap on the end or a rubber 'duck bill' shape. When your diff, transmission or transfer case is exposed to water it experiences rapid cooling which in turn causes the part to suck in air. A breather kit will help ensure that only air is sucked in, and not water which won't bode well with mechanical parts.