Thread is M6 withshaft at 7mm and the motor hole is for 3.17mm motor shaft but drilled it easily for a 4mm one. Perfectly balanced and machined. I have mounted a MasterAirscrew 10x7 propeller and it fits perfectly. Worth the price!Great light weight aluminum spinner for 3 blade propeller. Seems to fit tight on 4mm shaft. Cinch type adapter is part of the back plate. Works good! Looks Nice!!Can not find a better spinner for the price! Fit my 9x7 MASTER AIRSCREW props perfectly and the same with the EMAX BL2220/07 motors! One of the BEST purchases I have made from HOBBY KING!Nicely made for the price. I modified these to go on my ASP21A nitro engineI'll use it E-flite Bonanza.Looks to be drilled for 4mm prop shaft. I'm considering mounting this in my drill press and reaming the hole for 5mm.
Quality is OK, spinner looks nice. Does not fit 11x8.5 propeller blades, probably won't fit anything more than 6" pitch without grinding.
The spinner back plate is part of the prop adapter; the spinner can not be used with any other prop adapter as the hole in the back plate is large and tapered.Beautiful spinner for 3 blade props. Nice light aluminum construction. It comes with a clamp or crimp type adapter for what looks like a 4 mm motor shaft. The card that the package comes in says it's for 3.17 mm motor shafts, but I swear it looks like a 4 mm. It fit my motor perfectly and runs true without having to balance it.