So many great gifts, essentials, and gadgets are available at incredibly low prices on Black Friday and Cyber Monday, and stores are competing with each other for the best Black Friday deals—but not all these deals are as great as they sound. Some categories of items are known to have the lowest prices of the year during Black Friday, but others don’t have such great savings. Personal finance site WalletHub ranked product categories by the potential discount shoppers could get by buying items from each category on Black Friday. Sara Skirboll, shopping and trends expert at RetailMeNot, also has suggestions for what not to buy on Black Friday and Cyber Monday because lower prices for certain items are available later in the year. Together, their lists offer a pretty comprehensive guide to what’s a good deal—and what’s not—this Black Friday and Cyber Monday.