Twister B4 Bucking Machine - CartridgeSwappable Cartridge for Twister B4 Bucking Machine. Introducing Swappable Cartridges The Twister B4 allows operators the ability to remove and replace bucking cartridges on the fly, effectively reducing your downtime to near zero. When its time to switch strains or time for cleaning, swap in a clean QA approved cartridge and youre back up and running. No need to have multiple machines in waiting while others get cleaned. #gamechanger