Intel Pentium II 300
This Pentium II 300 used the 350nm 'Klamath'-core and is the fastest CPU you can get with this core. 'Klamath' formed the basis for the first Pentium II's released and was succeeded by the 250nm 'Deschutes'.
Not all Pentium II 300's are based on the 'Klamath' core, however. Some of the 300's are equipped with the newer and more energy efficient 'Deschutes' core.