|there's a little congealed lubricant stuck to the ZCI|
In the first picture, you can see the shape of the metal racks for each piston. ZCI's is a solid block, while SHS's flanges on the side mean that the rack is supported by a much larger portion of the piston body. This is important to prevent this from happening:
|rip ZCI piston, you weren't even being pushed that hard :(|
|swiss cheesing mine, did not come stock like that|
The support issue on the ZCI nylon may be "fixable" by epoxying the rack into place, but the ZCI polycarbonate costs the same and the SHS blue is only marginally more expensive and both would also benefit from the rack being epoxied in place, so why bother?