The first naturally insulated portable water bottle is the Reliance Green Glacier Insulated Water Bottle. Natural North American grown straw insulator, which you can see, has an transparent exterior shell that is made of tough aircraft windshield grade plastics. The unique cap design allows you to drink from either the smaller cap opening or the larger neck opening. Cap tab features a dual locking mechanism. First, it locks and seals liquid in when close. Secondly, it locks in the open position so it doesn't interfere when you drink. With the large neck opening it makes it easy to add ice and clean. The water bottle size is 24 oz.