How do I center my attack correctly?

The Mesh is not completly centered and I can't find the way of centering it good. Any way to get it perfectly centered?

 local ExpansivePart = Instance.new("Part", Folder)
               ExpansivePart.Name = "Shockwave"
               ExpansivePart.CanCollide = false
               ExpansivePart.Anchored = true
               ExpansivePart.Size = Vector3.new(.1,.1,.1)
               ExpansivePart.Position = tor.Position + Vector3.new(0,math.random(-1.8, -2.2),-0.25)

            local bubble = Instance.new("Part", Folder)
               bubble.Name = "Inner Ten"
               bubble.CanCollide = false
               bubble.Anchored = true
               bubble.Size = Vector3.new(.5,.5,.5)
               bubble.Shape = "Ball"
               bubble.Position = tor.Position + Vector3.new(0,0,0)
               bubble.Transparency = 0.6
               bubble.TopSurface = "Smooth"
               bubble.BottomSurface = "Smooth"

            local bweld = Instance.new("ManualWeld", tor)
            bweld.Part0, bweld.Part1 = bubble, tor

            local eweld = Instance.new("ManualWeld", humroot)
            eweld.Part0, eweld.Part1 = ExpansivePart, humroot
            eweld.C0 = CFrame.new(0,0,0)


            local Wave = Instance.new("SpecialMesh", ExpansivePart)
            Wave.MeshId = "http://www.roblox.com/asset/?id=20329976"
            Wave.Offset = Vector3.new(0, 0, 0)