We have a few different caps to choose from under the options. First is our 6″ standard black and clear cap that is nice because it allows you to see the coolant flow. Next is the Xlarge version of that cap with a 8″ opening that allows you to see through. These caps are nice, but they dont hold well to antifreeze well. Some last a year before cracking and others last multiple years. We carry both of these caps in a solid black textured pattern that hold up to anything and wont crack.
Next is our black and red ring with clear center. The clear center on these caps are made of a better material that holds up to the antifreeze. We have never heard of the clear center cracking on these. These caps are one of our best sealers and do not leak. We use a custom cut gasket on these to make a great seal.
Black hinged cam lock cap is a good option for race cars. They make it easy to add ice. They have a nice gasket on them as well, but will leak past the oring if filled too high.
Billet black aluminum cap. This is our best and nicest cap we have. We tried about four different types of billet aluminum caps and the ones we carry are the best by far. We do also have a custom gasket cut for these as well. These do not leak also.