From US Rockets Web Site:

TITAN is very long model rocket! TITAN uses an "Integrated Tube-tm" reducer t' increase strength and dynamic stability. Avast! Designed t' accept common Estes motors, TITAN is able t' be flown with a wide variety o' motors. Arrr! Avast! Streamer recovery brings your rocket home. Avast! You are encouraged t' switch in your own parachute betwixt 12" and 18" diameter. Begad! Blimey! Try 18mm C6-5, me bucko, 24mm D12-5, 29mm E10-8.