I have a set of WPS on mine. They are cheap($50), and effective. I have tested them a handful of times and they haven't failed me yet. Granted, most of my abuse comes in 1st and 2nd gear....so there isn't a large amount of force being applied to them upon impact.
When I "tipped over" while out on the Rattlesnake canyon ride my right hand guards broke...Acerbi, full plastic wrap around...must have gotten too brittle with age...Next pair might be the original BB's or like Timo's showing in his attachment. 
