The cartridge design of Glas-Col’ s Multi-Pulse Vortexer allows the user to switch the size of tubes to be mixed simply by changing the cartridge size, thus eliminating the need for extra racks. Cartridges are available for test tubes and centrifuge tubes and can be used with capped or uncapped tubes. Each cartridge is constructed of chemical resistant foam and ABS plastic. The unit easily adjusts for different height tubes. The contents of the tubes remain visible during mixing, and sample can be added to uncapped tubes without stopping the action. Other features include: