its not the 100cc (cos its not even 100cc in reality with Jabba 82.5 pistons)
mine are 83mm ones...
The difference is deshrouding the inlet valves closest to the cylinder wall, so for the low initial lift they can start to flow better. Bigger gap when rebored.
Thats the theory anyhows.
Only worth doing if you need block work/pistons or have the available funds IMHO.