The phrase "quality plastic" means that the plastic is made well, with good materials and careful manufacturing, resulting in a high level of durability and reliability. Full definition
The smartphone has a slim profile made of high quality plastic at the back in dual color which looks elegant. (pcquest.com)
The overall fit and finish on the car too has improved heavily with better quality plastics said to be used. (motorbeam.com)
A large amount of black plastic on the dash face and the lower - quality plastics used on the dash and door make the interior look a bit generic. (kbb.com)