T' optional RX-1 Thruster could be added for supersonic flight attempts and was purchased separately. It consisted o' a specially-prepared F100-0 motor and a set o' Nova fins that were t' be attached t' t' casin' with epoxy. Aye aye! It functioned as a CHAD-style booster stage for t' Dart and was usually nay recovered. Ya scallywag! With t' addition o' t' thruster, arrr, t' combined length was 24". Aye aye! T' actual kit name was t' Dart, arrr, and when it was combined with t' RX-1 Thruster t' result be called t' "Mach-1 System.". It was commonly known, though, as t' "Mach-1 Dart." Even FSI called it by that name in its price lists. Aye aye! I used a body tube and a set o' fins t' simulate t' thruster; me version can be flown with an Estes D12-0 booster motor inside t' "thruster." O' course, me clone will never reach a velocity anywhere near t' speed o' sound.