Spill proof lid yeah not quite [SEP] Cup seems very good quality. I bought this SPECIFICALLY for the spill proof lid. The slider part leaks like a sieve. I spilled hot coffee as soon as I started moving. NOT COOL. I'm really not happy but can't justify spending almost HALF of what I paid to send it back. MAJOR disappointment.<br /><br />***update*** 3/29/17<br /><br />So after my initial review on this cup expressing my extreme disappointment with the so-called spill proof lid, I was contacted buy a customer representative from Gus. He expressed his apologies and they ended up refunding my total purchase price even after I told them they didn't have to and sent me a replacement lid.<br /><br />Unfortunately they did not understand my complaint was not about the rubber gasket around the lid itself but the slider that covers the drinking hole. It is the slider that leaks because it does not seal. I informed them of my opinion on the design, which is I believe is a poor design for what is supposed to be a spill free top.<br /><br />Having said that, the Cup itself is absolutely fantastic. It's well-made and does indeed keep my coffee hot for quite a while. I have not tested it with cold yet. The way Gus stands behind their product definitely tells me that there concern is for customer satisfaction.<br /><br />They were very prompt and courteous. I really can't ask any more of them. I have put the rating up to 4. If nothing else it's  because of the simple fact they reached out to me to try and make it right. That to me speaks volumes of this company's commitment to ensuring their customers are happy. That's not something you see a whole lot of these days.<br /><br />If they can come up with a design that makes the lid truly spill free I would definitely buy this again.