ive tried some of the after market cdi units, only found one that performs as good as a stock unit, but never got any of them to outperform the stock unit on my fastest build which GPS'd 52mph on a bike with 24" wheels and a 30T sprocket. If youve got them that actually do add performance over a stock unit thats great. I have a Jake's Diamond head and I really like it, you'll need to find an extra long reach spark plug for it, i'm using an E3 3.22 in mine and it could actually use one a bit longer. the combustion chamber design of the diamond head is different than all the others, the squish ring in head is actually roughly 47mm, it doesn't have a flat surface for the head gasket to seal on like the other heads but instead the head gaskets bore diameter actually matches the squish areas diameter so the squish band is actually the exact height of the jug deck when a standard thickness head gasket is used and if a thin .016 gasket was used the heads squish band will actually sit down in the bore just a few thousands since the squish band is the same diameter as the bore and is beveled from the outer edge all the way in until it ends and the actual combustion chamber starts. this design is gonna make it easier for those who want higher compression to get it without having to shave the deck height down as much or none at all if they have a 40mm stroke engine, all they will have to do is order a .016 head gasket from juicemotors and they will get a higher compression ratio than they will with any of the other 6cc chamber heads ive seen. The diamond head is taller and a little heavier that the others, but I kinda like the looks myself, and I really like the squish band design, this head should really wick heat away from the jug also, only downside is that builds with tight space for the engine may not be able to run the taller head, but most all 26" cruiser frames and any full size fixie or mnt bike diamond type from will have plenty of room.