Baby Muslin Sleep Bag 0.5 TOG in Tanboocel® Viscose from Bamboo - Mermaids

The whole job of the lightest TOG: keep the cover on the baby and the heat off. This bag does the whole job.

Watercolor mermaids — the soft-pastel under-the-sea pattern.

This is the lightest sleep bag we make, rated for nursery temperatures between 75 and 81°F — summer nights, top-floor bedrooms, and homes that don't run central air. When a 1.0 TOG starts to feel like too much, this is the one you reach for.

Material. Tanboocel® Bamboo Viscose, blended with cotton and woven into open-weave muslin. Tanboocel® is a branded bamboo viscose made through a closed-loop process — third-party verified, with a lower water and chemical footprint than the generic bamboo rayon most brands quietly label "bamboo." It gets softer after the fifth wash than on day one, the opposite of how cotton ages.

The print. Ivory ground with watercolor mermaids in pastel pink and peach with brown hair, peach binding.

Construction. Sleeveless on purpose, so your baby sheds heat instead of trapping it. A two-way zipper runs the length of the bag, so a midnight diaper change takes seconds and wakes nobody. The neck and arm openings are bound in soft fabric, not scratchy serged edges, and cut snug — the part that matters most for safe sleep.

Why 0.5 TOG matters. Most premium brands skip this weight; their lightest options start at 0.6 or 0.7 TOG and run warmer than the label suggests. That leaves hot nurseries choosing between a blanket, which the AAP advises against, or no sleep sack at all. A true 0.5 TOG muslin solves both.

Need a warmer weight? The matching 1.0 TOG TENCEL™ Sleep Bag in Mermaids is built for the everyday 69–75°F nursery. The 2.5 TOG winter weight picks up below 68°F.

Sizing. 0–6M (fits 8–18 lb), 6–18M (fits 18–28 lb), 18–36M (fits 28–38 lb). Always size to current weight, not age. A neck opening that's too wide can ride up over your baby's face during the night, which is why a snug fit there matters.

Care. Machine wash cold and tumble dry low. Tanboocel® takes the dryer better than bamboo rayon, with less pilling and shrinkage over time. Don't bleach; iron on low only if you need to.

Safety & certification. AAP safe-sleep compliant. Tested to CPSC, CPSIA, and ASTM standards. Material certified to OEKO-TEX Standard 100. Loulou Lollipop is a Certified B Corporation.

Common questions

What temperature is 0.5 TOG good for?

0.5 TOG is the warm-room weight. Use it when the nursery sits between 75 and 81°F, typically summer nights, top-floor bedrooms, or homes without central AC. Pair with a short-sleeve bodysuit underneath.

Is muslin better than fleece for baby sleep?

Muslin breathes. Fleece traps heat. For warm-weather sleep, muslin moves humidity off the baby's skin and keeps temperature stable. Fleece sleep sacks are designed for cold nurseries and shouldn't be the default in summer.

Are baby sleep sacks safe for newborns?

Yes — once the baby is out of the swaddle phase and can roll. The AAP recommends wearable blankets like sleep sacks over loose bedding in the crib. Choose the correct TOG for room temperature and a size that fits at the shoulders so the bag can't slip over the face.

Browse all baby sleep sacks.

Free US shipping over $65. Free 30-day returns on unworn items in original packaging.

Part of the Big Dreams Sleep System. Sleepers and sleep bags in Mermaids are built to layer together through the night — same print, one system. Complete the set with the TENCEL™ 1.0 TOG Sleep Bag and TENCEL™ Sleeper.