This is a Puch hi hi head which I had to do some modification on to fit my engine. My wife's brother in law helped me with that. We had to cut the fins down because I have an expansion chamber from Arrow Cycles, and the head pipe sits over top of the head, so the tall fins of the hi hi head wouldn't fit underneath the Arrow pipe. We cut the fins down with an angle grinder and a very large cutting disc, and then I filed it to make the fins as straight as possible. There is a slight angle, but I got them as straight as I could. We also reamed out the holes for the head studs, because they come drilled for 6mm head studs and I have 8mm studs. I had a bit of trouble with tightening the head bolts because the socket wouldn't fit all the way down between the fins, so I took 4 axle nuts and used them as washers. This enabled the head bolts to sit up where they aren't between the fins. I am running 2 head gaskets, sprayed with copper rtv.