I took a chance on this, because I didn't think there was enough information in the description. I ordered the C version, with the 8x20mm motor, but unfortunately what arrived today was the A version, with 7x16mm motor, so the figures below are for the A version.

I haven't powered it up yet, but I think it will be very suitable for an indoor slow flyer of the Vapor, Ember, Cub etc. style. With the 8x20mm motor probably something a bit bigger and/or faster.

The prop has a diameter of 138mm, but no pitch marked. By comparing it with other props of known pitch I am guessing it is a 138x63 mm or 5425 inches. It came badly out of balance, but by taking tiny shavings off the heavy blade with a modelling knife, I eventually got it to balance perfectly. It is very light at 1.24g, and I don't think it would withstand a hard impact, but ideal for a slow flyer.

The description says it has a .8mm hole, but when I measured the prop shaft, it is 1mm diameter. I tried pushing it into the prop and it is a very tight fit, but does go in.

The gearbox is the usual two brass bush type, with plastic 9 tooth pinion and gear. I didn't count the teeth on the gear, but I'm guessing there are 54 giving a 6:1 ratio. The prop shaft is 27mm long with one end knurled for a length of about 8mm. I think the knurled end goes into the plastic nut provided, with the smooth end going into the prop, so you can remove and replace a prop without much trouble.

Weight of the gearbox is 1.29g and of the motor 2.61g. Motor shaft is 1mm diameter.

There is a square hole in the gearbox that I think is intended for mounting on the end of a square section carbon fibre rod, such as you might use for the fuselage of a very light slow flyer of the Vapor type. It looks as though it is a 2x2mm hole. It would probably be possible to mount the motor/gearbox other ways, e.g. with tiny cable ties or with glue.

The proof will be in how it runs, but at this stage I think it's a very light and economical power plant for an indoor flyer, with flexibility in the choice of motor according to your intended use.

Great micro motor for ultra light aircraft under 4 ounces. It ships unassembled but assembly is easy. The propeller balance should be checked and corrected before use. The gear is a little noisy at low rpm but it smooths out at flying speed. I used one in a Guillow's Lancer airplane I converted from rubber power to electric motor and 3 channel RC. This motor and propeller provide more than enough thrust for this under 50 gram airplane.