From the product description, check product page for current description, price and availability:

“The William’s Insulated Commuter Mug features double wall vacuum insulated 304 stainless construction, with copper in between the walls for even better insulation. The result is a mug that preserves more ice over a 26 hour period than the YETI® Rambler Tumbler.

This test was conducted by putting 13 ice cubes (6.6 oz of ice) in each mug and closing the lids and leaving the mugs at room temperature (approximately 68° F).  After 26 hours, the water was drained off and the ice weighed. (click on the thumbnail above for the results of our test).

In addition, it features a silicone sealed leakproof contained twist cap that keeps your lips away from plastic contact, resulting in a better drinking experience. The 16 ounce Commuter Mug is perfect for your home roasted coffee, as well as ice cold beverages, and of course, beer. Make your commute a little better, and keep something cold a long time for the weekend as well.