A lot of the deals on Black Friday appear too good to be true, so it should be of no surprise that many of them are.

The endless hype parade of Black Friday and Cyber Monday has created a bit of a momentum model when it comes to listing products. As Black Friday sales have grown — a 17% increase last year versus 2016 — the amount of products being listed includes a ton that are simply are not impressive deals.

JD Levite, a deal analyst for deal-finding site Thrifter and former Wirecutter editor, has been monitoring Black Friday for a long time, and has picked up on ways retailers mislead shoppers.

Products especially designed for Black Friday

The reputation Black Friday and Cyber Monday have is that of a day where a few things are dramatically discounted, which ends up being sort of a loss-leader for retailers. People come in the door for the crazy-good TV deals, and maybe they pick up a few other things while they’re in the store.

But in reality, TVs – the quintessential Black Friday purchase – are not always the discounted models you might expect. TV models do not have the same standardization or simplicity in offerings as other products, like computers. There is no Samsung “sVision 1” or the like, which is rolled out every year, similar to what Apple does with each iteration of its iPhone. Instead, retailers’ promotions list TVs that are identified by model numbers.

One of the reasons for that is likely because on Black Friday, manufacturers and retailers can sell a slightly different version of a standard model — the type that gets tested by professional reviewing sites — without people noticing.

“Everyone does this,” Levite told Yahoo Finance. “Manufacturers create special models to be sold on Black Friday. They’re similar, but maybe they won’t have bluetooth. Or they’ll have a dumber remote or cosmetic damage. They’re sold on Black Friday and retailers will discount them and say it’s a deal.”

Levite said it’s very hard for regular people to recognize these special products, but looking at the model number can tell you what you’re looking at, because they’re always different.

“You might go to Best Buy and see a Samsung NU7960. It’s very similar to MU8000 but the model number is slightly different. That should be a red flag in your head,” Levite said. Last year, for example, the difference was usually small between special Black Friday TVs and normal ones — fewer ports and no Bluetooth, for example — but different nonetheless.

Levite and others at his company said that these TVs often have “only sold at” in the listing. Looking at Best Buy’s current Black Friday “doorbusters,” for example, three TVs on the front page are listed as “Only @ Best Buy,” including the Samsung NU6070 and LG UK6190.