Change all Surface at once script help?

for num,tri in pairs(game.Workspace:GetChildren()) do
    if tri:IsA("Triangle") then do
    tri.BottomSurface = SmoothNoOutlines
    tri.TopSurface = SmoothNoOutlines
    tri.BackSurface = SmoothNoOutlines
    tri.FrontSurface = SmoothNoOutlines
    tri.LeftSurface = SmoothNoOutlines
    tri.RightSurface = SmoothNoOutlines
        end
    end
end

Its supposed to make all the items that are named "Triangle" in workspace to those Surfaces but it doesn't work, sorry for loops are not my best, any help?