This is a Giant 12x142mm rear thru-axle dropout conversion kit for use with 12x142mm RWS rear thru-axle.(73035). If you have a 135mm Q/R setup now and want to change to a 12mm thru-axle then this is your kit.
Drive and non-drive side dropouts
Buying Guide - Handbook
What to look for and things to consider before you buy