How do i change the size of the arms in this script?

Okay so this script is a first person arms script but whenever i try to change the size of the arms they get smaller instead of the size i wanted them to be.

wait(3)
lp = game.Players.LocalPlayer
p = lp.Character
p:WaitForChild("Body Colors")
larm = p['LeftLowerArm']
rarm = p['RightLowerArm']

l = Instance.new("Part",workspace.CurrentCamera)

l.FormFactor = "Custom"
l.BrickColor = p['Body Colors'].LeftArmColor
l.Material = "SmoothPlastic"
l.CanCollide = false


r = Instance.new("Part",workspace.CurrentCamera)
r.FormFactor = "Custom"
r.BrickColor = p['Body Colors'].RightArmColor
r.Material = "SmoothPlastic"
r.CanCollide = false


script.Parent.left.Value = l
script.Parent.right.Value = r



l.Size = larm.Size - Vector3.new(0.1, 0.11, 0.05)
l.CFrame = larm.CFrame

r.Size = rarm.Size - Vector3.new(0.1, 0.11, 0.05)
r.CFrame = rarm.CFrame


lw = Instance.new("Weld",l)
lw.Part0 = l
lw.Part1 = p['LeftLowerArm']


rw = Instance.new("Weld",r)
rw.Part0 = r
rw.Part1 = p['RightLowerArm']


r.Name = (lp.Name.."'s extra right arm")
l.Name = (lp.Name.."'s extra left arm")
while wait() do
    l.BrickColor = p['Body Colors'].LeftArmColor
    r.BrickColor = p['Body Colors'].RightArmColor


script.Parent.MouseButton1Down:connect(function()
    if l.Transparency == 1 then
        l.Transparency = 0
        r.Transparency = 0
    elseif l.Transparency == 0 then 
        l.Transparency = 1
        r.Transparency = 1

    else
    print("ERROR")

    l.Transparency = 0
    r.Transparency = 0
    end

end)

p.Humanoid.Died:connect(function()
    larm.Transparency = 0
    rarm.Transparency = 0
    l:Destroy()
    r:Destroy()
end)
end