This is hydrogen peroxide (H2O2) rocket engine parts. This engine powered with HTP (high-test-peroxide) and catalyst. Project contains nozzles and injectors for two different casing - for 40mm acrylic tube and 40mm PP reinforced water pipe.

More details on Youtube: https://www.youtube.com/watch?v=0UxtkTmbERs

For 40mm acrylic tube I use Integza's steam engine injector ( https://www.thingiverse.com/thing:4932849 ), so, it's not included. But nozzle is different - with interchangeble Laval bell variant (throat may be shrinked or expanded).

For 40mm PP tube I use screw mount for nozzle and injectors. This confguration with sealant is much more pressure-resistent solution than acrylic tubes. Also, this engine, depends on injector type, may be powered with bi-propellant (peroxide and watered catalyst), or with monopropellant (only peroxide) with "dry/solid" catalyst, stored in grains installed inside engine casing.

All hose connectors designed for 5-6mm silicone/pvc pipes (like this: https://aliexpress.com/item/1005002379462505.html ). I use mini 5V DC water pumps (like this: https://aliexpress.com/item/32898826601.html ). It's not a best solution, because it's better to get much more flow rate than it produces. It would be great to use external pressure vessel or turbopump to pump fuel into the engine.

Additionally project contains small fuel tanks (35/70ml).