Chamber selection:
HF21 - 17.4cc Stock compression
HF22 - 16.4cc (95+ octane)
HF23 - 15.5cc (100+ octane)
HF24 - 14.4cc (105+ octane)
Phathead Kits include a head shell with one combustion chamber, two sets of o-rings, cylinder head nuts, copper washers, some stickers for your bike and tool box and installation instructions..
Phathead cylinder heads are made of 6061 T6 billet aluminum. The material is stronger and transfers heat better than cast aluminum. The two piece design allows an increase in coolant flow as well as surface area which improves cooling for better consistency and performance.
The O-ring design eliminates the need to use a gasket. You can swap chambers without the cost of replacing gaskets.