Fold out to fill. Fold in when empty. This kit consists of two Pack-Up-Cups and one Pack-Up-Bottle. The Pack-Up-Cups hold 260 ml/8.79 oz and have attached lids to keep the right temperature in and bugs out. The Pack-Up-Bottle works with standard water filters, and has a sturdy loop to make sure the cap isn't lost and that carrying is easy. Of course, the whole kit is easy to clean and BPA-free.