Bar Keepers Friend uses oxalic acid as its main cleaning ingredient. Ajax and Comet use bleach (trichloroisocyanuric acid). Oxalic acid is more effective than bleach on mineral deposits and rust stains. Plus, each product uses different surfactants. Ajax uses sodium dodecyl benzene sulfonate, Comet uses alkylbenzene sulfonic acid, and Bar Keepers Friend uses a combination of benzene sulfonic acid, mono C10-16 derivatives, and sodium salt. Read this comparison of Bar Keepers Friend vs. Comet to learn more.