I bought this because my last one exploded off dramatically, and it seems like nice pieces of metal (and plastic). It does not come with any assistance, though, in terms of assembly, so I copied the picture, but there doesn't seem to be any way to make the spring a functional part of the design? I can use the only bolt to attach it to my bike and it will dangle there, but that does not help my chain. Right now it is sitting on my shelf where I can look at it and remember how nice it was when I could pedal.
maybe it is good? I will never know 
