Helicopter size

Common question: Is a 50 size and 600 the same? That is a good question and one I have to explain a lot. Basically the general unofficial rule is you specify blade size if the helicopter is electric and engine size if it is nitro. However the problem is not everyone follows a standard.

Here is a list:
60 size, 90 size, and 700 class all use main blades around 700mm.
50 size and 600 class all use main blades around 600mm.
30 size and 500 class all use main blades in the 500 range, typically around 550mm.
Now here comes some of the confusion...
Align 700 is a 90 size nitro.
Align 600 is a 50 size nitro.
Align 550 is a 500 class electric using 550mm blades.
Align 500 is a 400 class electric using 425mm blades.
Align 450 is a 300 class electric using 325mm blades.
Another trend lately is to just use the first number. The Compass 6HV and MA Furion6 both use only the number 6 to indicate a 600 class electric.
BTW: In case you didn't know, when a nitro helicopter is referred to as 30, 50, 60, or 90 size, that is related to the combustion volume of the engine. A 90 size helicopter uses a nitro engine with a 0.91cu in combustion area.