If you’re not familiar with vermouth, it’s wine that’s been fortified (usually with a bit of brandy) and aromatized with herbs or spices—and though it has a longer shelf life than non-fortified wine, it needs some TLC. But it’s worth it: Bartenders know that vermouth is a secret weapon to add body and nuance to martinis and other cocktails.

“The key to a great martini is fresh vermouth,” insists John Dye, proprietor of Bryant’s Cocktail Lounge in Milwaukee, WI, known for its classic martinis and Vespers. “We go through a lot of vermouth, so ours is always fresh.”

Traditionally, dry vermouth (also known as white or French vermouth) is used for a classic martini, while sweet vermouth (also known as red or Italian vermouth) is used in the old-school Martinez, as well as whiskey-based drinks like the Manhattan.

Dolin Dry Vermouth: Crisp and classic, its relatively neutral flavor profile makes it ideal to pair with London Dry-style gins like Tanqueray and Boodles or vodka. This is the dry vermouth of choice at Bryant's.

Cocchi Americano: Technically an "apéritif wine" rather than a vermouth, its fresh, mild sweetness complements gins with fruity or floral notes, such as Nolet's and Hendrick's. Also works well to sub for Lillet in Vespers.

Perucchi Vermouth Blanc: This delicate, slightly herbal Spanish vermouth stands out next to gins that play down the juniper, such as Aviation and Plymouth, or vodka. It's also refreshing in a Spanish-style vermouth spritz.

Imbue Bittersweet: Made in Oregon, this artisanal vermouth is off-dry and herbaceous, with a pleasing chamomile-sage aroma. It stands up to robust-flavored gins like Junipero or barrel-aged gins, or the umami punch of a Gibson.

Carpano Antica: Rich, complex cocoa, port, and spice notes finish with a bracing bitter edge. Try it in a Martinez, especially with Old Tom-style gins such as Hayman's or Ransom Old Tom Gin.