Each lid has a valve you can use with our electric vacuum pump to draw out the air and help food stay fresh longer.
The containers aren't designed to be industrial-grade airtight: they slowly lose vacuum over a few days, which is about how long fresh food is usually kept. If one container loses air much faster than the others with the valve closed, write to help@ziruma.com with your order number.
The valve is a standard 1-inch size. We haven't tested third-party pumps, so we can't guarantee they'll work with our lids.
Tip: make sure the silicone seal on the lid sits facing down; otherwise the pump can't draw out the air.