If they have a cartridge he's wrong about them being Katana forks, they are GSXR.
He's right about them being 41mm though. 600 and 1200 Bandit use 43mm forks
Katana is basic damper rod, (although it has click adjuster which doesn't seem to do anything ) GSX-R has internal damping cartridge, I think 1998 or 2000 used conventional style with cartridge, the others are USD
Katana forks - the adjuster turns a washer under fork spring, damping is fixed rather than variable