The most commonly used is 1.0, 1.5, 2.0 and 2.5mm aluminum wire
For small trees you need 100g per strength, for larger 250g
The bonsai wire must be thick enough to hold the branch in place
At the same time the wire must be thin enough to work with it
Aluminum wire must be about half the thickness of the branch
Copper bonsai wire must be about half as strong as aluminum
Different strong branches need different wire thickness
If a wire is too weak, a second wire can be wrapped arround branch
A strength can be used for 2 branches if they are the same thickness
The wire length must be about 1/3 longer than the branch