Find Model size using script?

So lets create a completely random model, just for an example:

local model = Instance.new('Model', Workspace)  --Makes our model

for i = 1, 20 do
    local part = Instance.new('Part', model)  --Creates a part
    part.Anchored = true
    part.Size = Vector3.new(math.random(1,50), math.random(1,50), math.random(1,50))  --Random size
    part.Position = Vector3.new(math.random(1,50), math.random(1,50), math.random(1,50))  --Random positions
end

We have no clue what the size of the model is, so you can try this at the end of that script:

print(model:GetModelSize())

Give it a shot, and let me know if I need to elaborate.