My search for good indoor/outdoor slippers has been in progress for several years. I hoped these would be the solution, but alas they are too tight. My *measured* shoe size is 44.5 4E Euro, or 10 1/2 Extra Wide. Despite my misgivings, I followed the Gumbies sizing guide and ordered a pair in US 11. They do not fit well, and squeeze my feet. I will not return them because I am not that guy, but cannot recommend these slippers to folks like me with oversized feet. If you should decide to take a chance, I'd advise you ignore the "true to size" description in the sizing guide and order the next size up.
The construction is solid, so if you wear a regular width shoe perhaps they will work for you, but for me, I will not wear mine for more than a short time before they become uncomfortable. I also ordered a pair of Outback slippers at the same time which are sized similarly. The open back design of the Outback model allows the foot to move back to find more space. Less snugness, but the heel then moves off the end of the footbed so they have comfort issues as well. Lesson learned: if you require extra wide shoes and the maker doesn't offer wide widths, order a larger size no matter what a manufacturers sizing guide says.