This is a 54mm 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 (K), to purchase this motor you must be Tripoli, AMRS or ARA level 2 certified (or attempting a level 2 certification).
K850 Dark Matter™ DMS™
Motor K850 Manufacturer Aerotech Type Single Use (Disposable Motor System™) Flame Dark Matter™ (DM) - (Sparky) Quantity per pack 1 motor Diameter (mm) 54.0 Length (cm) 63.5 Ejection Delay (s) 16 Average Thrust (N) 922.0 Maximum Thrust (N) 1094.0 Burn Time (s) 2.0 Total Impulse (Ns) 1869.0 Total Mass (g) 2041 Propellant Mass (g) 1224