This is the seal the rear side 1/4 window slides down though .. but this is only on the 68-72 series below.

This is a  USA Made Seal, a good quality restoration part... and has a stainless Steel Core.  You can buy cheaper but not better then this one.

This part also fits the following autos:
1968 PONTIAC GTO
1968 PONTIAC LEMANS
1968 PONTIAC TEMPEST
1969 PONTIAC GTO
1969 PONTIAC LEMANS
1969 PONTIAC TEMPEST
1970 PONTIAC GTO
1970 PONTIAC LEMANS
1970 PONTIAC TEMPEST
1971 PONTIAC GTO
1971 PONTIAC LEMANS
1972 PONTIAC LEMANS