Why does the +vector3.new/-Vector3.new not work?

local enabled = true
Player = script.Parent.Parent
character = Player.CharacterAdded:wait();
mouse = Player:GetMouse()
Run = game:GetService("RunService")
Head = Player.Character.Head 
function onKeyDown(key)
	key = key:lower()
	if key == "r" then
		game:GetService("Chat"):Chat(Player.Character.Head, "REN!")
		r = Instance.new("Part")
		r.Shape = "Ball"
		r.Transparency = 0.7
		r.BrickColor = BrickColor.new("White")
		r.TopSurface = "Smooth"
		r.BottomSurface = "Smooth"
		r.CanCollide = false
		for i = 1,20 do
		r.Size = Vector3.new(r.Size.X + 1, r.Size.Y + 1, r.Size.Z + 1)
		wait()
	end
	    for i = 1,20 do
		r.Size = Vector3.new(r.Size.X - 1, r.Size.Y - 1, r.Size.Z - 1)
	end
		r.Parent = workspace
		Weld = Instance.new("Weld")
		Weld.Part0 = r
		--Weld.C0 = r.CFrame:inverse
		Weld.Part1 = Head
		Weld.Parent = character 
	end
end

mouse.KeyDown:connect(onKeyDown)

Thanks for helping me.