[Greg Needel]

I have used both the aluminum omnis and the plastic ones, I recommend the plastic ones over the coolie dualies or aluminum just because of bearings. The molded omnis hold 2 bearings in for full support while both of the other kind require you to put a bearing in the attached sprocket. Just for ease of use the molded ones save you the trouble of finding flanged R6 or R8 Bearings.