High quality product. Beautifully made, looks like an original Warwick part. Fitting and adjusting it was a simple, 15 minute procedure. It works exactly as advertised. I can now flip my low E string to a low D and back, at will. A little expensive, but still highly recommended if you need to switch to a Drop-D tuning occasionally.
So you love your 4-string but want to play a low D occasionally? Whack this baby on and you're away! Literally one screw and 5 minutes to install! Really useful and extremely well made - a bit pricey, but cheaper than a five string!!