This addition is a must for UK canning. In the UK it is difficult to have canner gauges calibrated, we should do them every year. Gauges can, over time, become faulty. The jiggler weight will always jiggle at the correct pressure, regardless of what your gauge says. The 15lb weight that comes with the Presto 23qrt canner relies on the gauge being accurate. It also takes some skill and patience to hold the correct canning pressure, and constant supervision. The jiggler allows you to free up some time from constant canner watching.