An ordinary water bottle cap will fit any Platypus bottle https://www.platy.com/bottles-storage (by the wonderful Cascade Designs who also make the absolutely best Sleeping Pad: https://www.thermarest.com/mattresses/womens-neoair-xlite). You can make holes with a large needle (doll needle pictured – much safer). With nine holes as pictured one litre lasts 6 ½ minutes. I usually carry one 2