While the SL R129 isn't used in winter ( salt ) or taken out if it is raining ( I don't want to clean it ) , I am not afraid to drive it if it starts raining, the factory blade is just fine and I'm pretty sure it is the same as a W124. The factory blade has a circle that changes from black to red when it has seen enough UV, and there is also a white MB star on the blade.

I tried a brand name aftermarket but it didn't have a way to keep the blade from coming off the hook. It was setup for a bump on the hook where the SL had a notch. The factory blade was actually less $ than a discounted mail order aftermarket.