Suspension ?

What is the difference between pillowball mount and non-pillowball mount coilovers?

The pillowball mount removes the rubber bushing and it's compliance from the upper shock mount. This has a small benefit for suspension responsiveness (not noticable in normal driving) and a small downside in the form of increased noise and harshness (both a little noticable in normal driving). There really isn't much of a reason to use them on a normal street car, except for the fact that they make install VERY easy as you never have to disassemble the stock coilover to install the new one.