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. It functioned as a CHAD-style booster stage for t' Dart and be usually nay recovered. Begad! Blimey! With t' addition o' t' thruster, t' combined length was 24". T' actual kit name be t' Dart, and when it be combined with t' RX-1 Thruster t' result was called t' "Mach-1 System.". Aye aye! Blimey! It was commonly known, though, me bucko, as t' "Mach-1 Dart." Even FSI called it by that name in its price lists. Ahoy! Blimey! 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.