This 0.5 liter is also ideally suited for small bags. Break-proof, tasteless, stable, easy cleaning and dishwasher proof and "nothing dripping" closure. So must be a water bottle today.
For unilaterally supported smaller bags which is an ideal size (also wg. The weight!).
The One-hand clamping closure head of the 0.7 liter can not be screwed on the 0.5 liter, as too large.