With the D20-4 we got to 170m on the Estes Green Egg - great engine for a 24mm motor with a 24mm to 18mm adapter, and also suitable for larger diameter models with an 18mm motor mount. Decent smoke, louder sound compared to the Estes D12 (this engine has less than half the burn time!). If you use D12-5s this is nice alternative with an adaptor. Use both! Some minor chuffing on the pad (probably should be expected for the Q-Jets), but initiator does the job and the nozzle holds up.

I like the fact this motor has D impulse in a 18mm casing. These composite motors pack a good punch.