Carry-on-only travel lives or dies at the liquids bin. Buy the wrong toiletry bottles and you're either surrendering your shampoo at security or scrubbing leaked conditioner out of your bag. The fix is a set of small, refillable, leak-proof bottles that fit the 3-1-1 rule. This guide covers the rule itself, why silicone bottles win, how to refill and label them, and what actually counts as a liquid.
1. The 3-1-1 rule
In the US, carry-on liquids follow what the TSA calls the 3-1-1 rule. It's easy to remember once you break it apart:
- 3.4 — each container must be 3.4 oz / 100 ml or less (it's the container size that matters, not how full it is).
- 1 — all your containers go in one quart-size (roughly 1 liter) clear, resealable bag.
- 1 — one bag per passenger.
Rules vary and change. Other countries and airports have their own limits and screening tech, and requirements are updated from time to time — always check the TSA and your departure airport before you fly. For the full breakdown, see our TSA liquids guide.
2. Why silicone bottles win
The travel-size bottles from a drugstore are cheap, but they're stiff, hard to squeeze empty, and prone to popping open. Purpose-made silicone travel bottles (the squeezable GoToob-style kind) solve most of that.
- Leak-proof by design — good ones use a valve or sealing disc so pressure changes at altitude don't force product out.
- Squeezable — soft silicone lets you push product out and get the last bit, instead of shaking a rigid bottle.
- Refillable and durable — wide openings make them easy to fill and clean, and they survive many trips.
- Under the limit — sold in sizes at or below 3.4 oz / 100 ml so they're compliant out of the box.
| Silicone travel bottles | Drugstore travel bottles | |
|---|---|---|
| Leak resistance | High — valve/seal designs | Variable; can pop open |
| Ease of use | Squeezable, easy to empty | Rigid, harder to squeeze |
| Refill & clean | Wide openings, reusable | Narrow, often single-trip |
| Longevity | Many trips | Short-lived |
3. Refilling and labeling
A refillable set only helps if you can tell the shampoo from the conditioner at 6 a.m. in a dim hotel bathroom.
- Don't overfill. Leave a little headroom so the bottle can be squeezed shut and so air can expand without pushing product out.
- Label clearly. Use the included tags, a write-on panel, or waterproof labels — color-coding caps is a fast shortcut.
- Fill over a sink and wipe the threads before closing so the cap seals cleanly.
- Bag them anyway. Even leak-proof bottles go inside your quart bag — that's both the rule and cheap insurance.
- Wash between trips to avoid buildup, especially with thicker products.
4. What counts as a liquid?
The 3-1-1 limit covers more than obvious liquids. If something can pour, spread, spray or squeeze, screening usually treats it as a liquid or gel:
- Yes, it's a liquid/gel: shampoo, conditioner, lotion, toothpaste, sunscreen, liquid foundation, gel deodorant, mascara, perfume, and aerosols.
- Usually fine as a solid: a bar of soap, a solid stick deodorant, powders, and lip balm — solids aren't liquids, though very large powders may get extra screening.
- Special cases — medications, baby formula and similar are often allowed in larger amounts but must be declared; check TSA rules for exceptions.
Switching some items to solids (bar shampoo, stick sunscreen) frees up room in your quart bag. For the rest, keep everything to 3-1-1 and pack it where it's easy to pull out at security — see our packing list and packing cubes guide.