I guarantee my media to play without skipping. Typically when I sell disk based media valued under $20 I label it as only one of two conditions; “good” or “acceptable”. The disks will most likely have some scratches and may have been polished. 

If condition is “Good” Game will have the manual included, but may not have all inserts, posters or maps.

“Acceptable” disks may have more prominent scratches than “good” but are still guaranteed to play, game manual may not be included, The cover art may have some damage.