Help with CFrame:ToWorldSpace?

I am trying to create a part that spawns on the side of another part, someone has told me to use CFrame:ToWorldSpace. I used it, and it worked fine when only placing one part. then, I tried adding a second. when I did the first part was placed correctly, the second part was in the wrong spot. I do not know why, here is the code:

local Part = script.Parent

local Pos = Part.CFrame

local Size = Part.Size

local Arrow = Instance.new("Part")

Arrow.Parent = script.Parent

local SizeX = Size.X * 1/2

Arrow.Anchored = true

local FinalPos = SizeX + 1

Arrow.CFrame = script.Parent.CFrame:ToWorldSpace(CFrame.new(FinalPos, 0, 0))

Arrow.Size = Vector3.new(0.5, 0.5, 0.5)

local Part = script.Parent

local Pos = Part.CFrame

local Size = Part.Size

local Arrow = Instance.new("Part")

Arrow.Parent = script.Parent

local SizeX = Size.X * 1/2

Arrow.Anchored = true

local FinalPos = SizeX - 1

Arrow.CFrame = script.Parent.CFrame:ToWorldSpace(CFrame.new(FinalPos, 0, 0))

Arrow.Size = Vector3.new(0.5, 0.5, 0.5)

anyone know why this does not work? thanks in advance, me7474.