5 mm headphone output. The strap between the toes is leather, a bit stiff and I know it’s there. Alot of mules are too wide. Better instructions on how to put them on or at least a video on YouTube or a link where we can view it. Now that Ive used it for a few weeks, I can honestly say its likely one of the best keyboards Ive ever used. I like pairing a bigger earring with a smaller one for my second piercing and these are perfect for that. These are THE most comfortable pajamas I have ever owned, so soft and cozy. These fit perfectly! When I started working with it my first thought was "OMG it looks like the 90s threw up". I love the accompanying charging case as it makes for easy transportation and storage.