Here are some examples of damage that may seem small but comes with major damage. Often times, metal tools like vise grips or channel locks are used to hold the piston shaft when assembling a coilover. This can put small scratches/gashes in the shaft itself. As the damper compresses and decompresses, it’ll prematurely wear out and seals or o-rings inside of the the damper itself. Damage like this is generally not covered under any manufacturers warranty since the case is usually some sort of improper technique during installation. Professional installation is required!