Quality:
These switch covers are printed from Acrylonitrile Butadiene Styrene (ABS). ABS is a high temperature plastic that can withstand high temperatures found in aircraft cockpits and is used extensively for aircraft trim pieces by OEM manufacturers (Cessna, Piper, Mooney). 

Installation:
These snap on and do not require any adhesive, just like the original. 

Often, glue or Velcro is often found in between the old, broken covers and the switch pad. These should be removed for a good fit. 

Due to age, abuse, and variances in Klixon switch assemblies, we've found that the switch covers fit more loosely on some switches than others. This is normal - the cover will not fall off. If desired, a dab of white RTV can be used between the switch and the cover.  

These are not FAA/PMA'd parts and hold no airworthiness approvals. 

As such, per FAR 43.13(b), the installer must determine if parts and materials are "of such quality, that the condition of the aircraft, airframe, aircraft engine, propeller, or appliance worked on will be be at least equal to its original or properly altered condition (with regard to aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness."