The main technical difference is the internal diameter of the main motor tube, The UK supplier for aluminium tube produces a tube in slightly different inner diameter, this means the nozzle and injector housing have a smaller diameter than Rene's (only a fraction of a millimeter) If you want spares producing for a Micro hybrid bought from Rene just specify this and I can produce the part to fit. 

The main functional difference is in the inner diameter of the injector ( the hole the NOX is injected through) and the shape and throat diameter of the Nozzle has been refined slightly.

The other main differences between a micro hybrid purchased from Rene and Me is Mine is Pre-Made if required and Pre-made ones come anodised. 

Directly compatible parts include the injector, O rings, circlips, burst disks, Paper Fuel, Hex Key and initiator bolt.

The following have slight diameter differences but can be produced for either Rene's or my micro hybrid nozzle, injector housing, T-Nut and Nylon Fuel.

The following can only be suppled for my micro hybrid motor body tube.

Preheater

Nitrous oxide has to be heated to 500^OC to start it breaking down to release the oxygen this is the function of the pre-heater to start the initial breakdown until the fuel is starting to burn.

The pre-heater in the micro hybrid is also used to burn through the burst disk to initiate the flow of nitrous oxide.

Nitrous Oxide

In hybrid engines the fuel and oxidiser is kept separate until ignition and then the oxidiser is injected to the fuel chamber. The nitrous oxide for the micro hybrid is contained in ISI whipped cream charger bulbs each bulb contains 8g of N₂O

Burst Disks

Burst disks are precision cut from P.E.T.E Plastic the thickness of this is important as if it it to thin it will not hold back the NOX and may rupture prematurely, if it is to thick it may not rupture at all.

Hybrid Combustion Process Principal

A generic hybrid rocket works by burning an inert solid fuel grain in the presence of a gaseous or liquid oxidiser, for model rocketry this tends to be Nitrous Oxide as it is easy to handle and relatively easily obtained.

The process of burning an inert fuel with the oxidiser is very similar to the way a  candle burns, as shown below:

In a hybrid rocket the oxidizer flows down a port  or ports in the solid fuel grain and reacts with the solid fuel. This produces the hot exhaust gases required to produce thrust. This process can be seen in the following image:

The oxidizer and the solid fuel are able to react, because the hot gases from the combustion process cause a small layer of the fuel to vaporise. This fuel then reacts with the unused oxidizer to produce more combustion gases. This process is shown in the following image:

It is important to get the correct flow of oxidiser, if the flow is too low the flame will not be able to develop and may even go out. If the flow is too high it can blow out the flame. This can be shown by the example of putting candles in a tube and blowing down the tube. as depicted below: