In 1984 the thread changed in most (not ALL but most) Camaro Firebird TA's with DRUM rear brakes to a metric thread.. not all but most.
This is for the 1984-92 ..METRIC and any that may have had a AF thread for some reason use the earlier 82-83 version.... DRUM BRAKE REARS ONLY
THIS IS FOR 1984-92 with METRIC threads... two brake lines. pre bent ready to install.