The most commonly used characteristic is the tooth count.
A vernier caliper would be my choice for measuring the thickness of the sprocket (which has to work with the width of the chain) for which there are several options available depending on bike/drivetrain type.
the 3rd size it can be helpful to know is how the sprocket attaches to the hub. Again several options available. But knowing which kind of drivetrain it is should usually be enough to get you the right part.
13t driver goes on a 33t sprocket
Sprocket size will b 16T & 39
Usually the sprocket is an inseparable part of the freewheel, and the size of the freewheel is determined by the hub.
The chain is size 530, and the stock gearing is 15/45, meaning that the front sprocket has 15 teeth and the rear sprocket has 45 teeth.
The recommended size of the chain to use with a small sprocket is typically a smaller chain size to ensure proper fit and function.
It uses a 47 tooth sprocket.
Either increase the size of the front sprocket or decrease the size of the rear sprocket. This will change the gear ratio and make the scooter faster. Although you need to kick harder to start the scooter. Also, I do not know of any sprocket mods available online so you would probably have to get it custom made which may be pricey.
Any size will work. What'll work best depends on what you want it for. Higher top speed - go for a big sprocket. Quicker off the start - go for a smaller sprocket.
The primary sprocket nut is 1 - 1/8 inch.
a 25 tooth sprocket will fit on a 9 tooth driver
43/16
If the driver/freewheel isn't too badly worn you can keep using it even if you replace the sprocket.