The sight glass doesn't look like one for a mustang. I got this from a Mustang shop awhile ago with the other hose and the elusive AC bracket that hold them together at the shock tower brace. True it could be a replacement sticker. But don't know for sure. The engineering number on the auction site is C4AA. I thin Mustangs start with C4ZA. The other hose might be for a six cylinder since it appears to be too long for a V8...I'm sure others might know more...