You can save a lot of money if you’re buying a new TV on Black Friday, but there are a few things you need to know about first.

I was just shopping for a new TV. I don’t really need a new one, but the prices are so low that I thought I could replace my aging 1080p TV with a new 4K one of the same size, while only spending a few hundred dollars.

Best Buy, for example, has several 4K TVs that are priced between $350 and $700, which is really attractive considering you’re getting a sharper resolution on a big screen. But know this before you buy those TVs.