This is a 38mm diameter single use motor. It is ready to fly and doesn't need any motor hardware. You will still need a retaining system.
Because of the impulse class (H), to purchase this motor you must be Tripoli, AMRS or ARA level 1 certified (or attempting a level 1 certification).
H550 Super Thunder™ DMS™
Motor H550 Manufacturer Aerotech Type Single Use (Disposable Motor System™) Flame Super Thunder™ (ST) Quantity per pack 1 motor Diameter (mm) 38.0 Length (cm) 20.6 Ejection Delay (s) 14 Average Thrust (N) 552.0 Maximum Thrust (N) 640.0 Burn Time (s) 0.6 Total Impulse (Ns) 312.0 Total Mass (g) 316 Propellant Mass (g) 176