This extra test lid is for the 7103 Micro-Bath, because, occasionally you need a lid with holes drilled in it and sometimes it is essential a lid that is completely sealed. For calibration, it is convenient to drill a pattern of holes into a test lid to keep the bath sealed during calibration for optimal constancy, and to confirm probes are properly spaced from one another and go into the bath vertically. However, you also want to have a lid that prevents spilling when you are carrying the bath from the lab or shop to the test site, so we recommend keeping a spare lid to use during testing. That way you can have ideal test conditions and a clean work environment.
