...The 914-6 GT's were equipped with either the 911S Alloy calipers or, the more high performance oriented 908 Alloy calipers. Some 908 calipers were actually cast out of magnesium on an experimental basis and not many of these samples can be found today. The biggest difference between the 911S Alloy and the 908 Alloy calipers is that the 908 has the "quick-change/release mechanism" to R/R the brake pads very quickly and a deeper recessed area to accept "thicker" brake pads. The thicker brake pads were used in the 908 racers to minimize pit stops during endurance events...