Rust-proof stainless steel water bottleThe underside on the cap is hollow, so this bottle can hold over its advertised 18 ounces (we in shape 21 ounces of liquid after we crammed it to the brim). Michael Hession/NYT WirecutterIt suits like a glove in a lot of slip pockets meant for documents (as a result the A6 within the title) or tech products. O