Consider your style preference
Remember: The smaller the barrel, the tighter the curl. So if you’re looking for something to help straighten out your hair or achieve that wispy curtain bang look, go for a large round brush between two and three inches wide. And if you’re looking for something to flip out your ends or get curled layers, go for a narrow round brush under one inch or less in diameter. Meanwhile, if you want the best of both worlds, try a medium-sized round brush around one or two inches wide to smooth out your hair while creating some volume at your roots, says O’Connor.
Keep your hair texture in mind
Tailor your round brush to your hair texture, says Harper. A classic boar-bristle round brush (or any round brush with natural bristles) can be good for fine hair, thick hair, and curly hair—basically, anyone who wants to stretch or straighten their hair. Meanwhile, a round brush with a mix of natural and plastic bristles can help detangle and smooth coarse hair without as much snagging and yanking.
Look for additional features
Got long or coarse hair that takes forever to blow-dry? Try a round brush with a vented ceramic barrel, which helps retain heat and speeds up drying time. If you’ve got fine hair and want to add a lot of volume and bounce, O’Connor says you may want to try a large metal round brush, which “can help mimic a curling iron, giving hair more staying power.”
Just make sure to avoid brushes with tips on the ends, says Harper: “These tips can break off, and the sharp plastic underneath can tug at your hair.” Instead, look for a brush that has a mix of natural and plastic bristles without the little balls at the end to avoid any potential tangling.