"Refletance is not a valid member of Part" Can someone help me?

i had first an error with this script someone help me fix it but when i fix the first problem another error happen the output says "Refletance is not a valid member of Part" and idk what does it means if someone of you guys know it please help me fix it i want to learn scripiting but im still a noob at it so idk so much about it ill let the script down if someone can help me please!

Here is my code:

local Player = game.Players.LocalPlayer
repeat wait() until Player.Character
local Character = Player.Character
local Mouse = Player:GetMouse ()

Mouse.KeyDown:connect(function(Key)
 if Key == "t" then
        Character["Left Arm"].Transparency = 1
        local LeftArm = Instance.new("Part")
        LeftArm.Name = "BusoLeftArm"
        LeftArm.BrickColor = BrickColor.new("Black")
        LeftArm.Material = "SmoothPlastic"
        LeftArm.Refletance = 0.2 -- the output says that the error is here
        LeftArm.CanCollide = true
        LeftArm.Anchored = false
        LeftArm.Size = Vector3.new (1, 2, 1)
        LeftArm.Parent = Character
        local w = Instance.new ("Weld")
        w.Part0 = Character["LeftArm"]
        w.Part1 = LeftArm
        w.Parent = LeftArm
    end
end)