Flannel is a woven fabric that has long been a staple of sleepwear. It insulates well on chilly nights and breathes better than fleece, which tends to trap heat. It’s also more durable than cotton and polyester sleepwear, and retains its soft feel over time. Some manufacturers double- or even triple-brush flannels for added softness.

Men’s flannel pajamas typically feature a button-front shirt and drawstring pants with a relaxed fit. They’re available in a variety of plaid patterns, and some styles are tailored for a slimmer silhouette. Most flannel pajama sets are made from either 100 percent cotton or 100 percent wool, which has the advantage of being more breathable. You can find flannel sleepwear in lightweight and midweight options, as well as heavier styles that may be suitable for year-round use.

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Many flannel sets come in a range of sizes, including regular, petite, and tall. Some sellers provide size charts for their products, which can help you choose a set that fits well. Some manufacturers offer pajamas in a range of colors, as well.

For a classic two-piece combo made from sustainably and ethically sourced materials, consider Pact’s Fireside Flannel Sleep Set. It’s crafted from 100 percent organic cotton and sustainably sourced in accordance with the Global Organic Textile Standard. Its short-sleeve top and drawstring shorts are brushed on both sides and yarn-dyed to prevent fade over time. They’re machine washable for easy care. The set is offered in a variety of sizes for adults and kids, and it can be personalized for an additional fee.