A hydraulic bicycle brake usually contains either DOT fluid or mineral oil. Over time, the fluids in your brakes attract moisture and dirt from inside the brake system. Changing the fluid in your brakes regularly will ensure that you maintain good braking performance and that your brake system feels better and lasts longer. If you are going to change the brake fluid in your bicycle brakes, it is very good to have a so-called bleeding kit. With this kit you can easily change the fluid in your brakes. You can find aeration kits here with us.