This hot water bottle is made using bulky/chunky yarn – suited to an 8mm/L crochet hook. Alternatively, two strands of DK/8ply yarn can be worked together for similar effect. Instructions are included for a 2.5-liter hot water bottle and a 1.75-quart (2-liter) hot water bottle. A side zip can be included to provide easy insertion and removal of the hot water bottle, or alternatively, insert the (rolled-up) hot water bottle through the top opening.