The model and style of the laboratory mixer has a great deal to do with how many test tubes or samples can be mixed at one time. Smaller units typically offer options for 8 test tubes and 16 or more slides, while the larger double tray models could provide options for up to 30 test tubes at one time. Keep in mind that the larger units will provide greater option to use this equipment with larger samples and test while still taking up approximately the same area on a workstation or counter top. Different machines may also offer larger or smaller numbers for test tubes depending on the size of the tubes themselves. The pad, which is typically reversible, will have grooves or indentations to cushion and hold the test tubes, slides or sample containers on the laboratory mixer while it is in use. To avoid spills and possibly test tubes sliding or falling off the pad it is essential to only use the tubes the laboratory mixer was designed for. Smaller tubes typically won't cause a problem but larger tubes may not stay in the holders, resulting in the need to re-run test costing both time and money.