Ideally, you want you heal to be just short of the back stitching, to get the max cushion. This is a pretty high quality roller bike trainer! At this price point this should not be happening. For the second time I have received the incorrect size and colour shoes. 3) Durability - The moment you hold this mic you can tell that it is well built. Im a total Birkenstock convert, some joint problems halved wearing Birkenstocks in general. Personally I would advise against this purchase even for 5$. Ill add comments when I get a working set back. Comfort level in the ear is great and I can put them in or take them out by the stem and therefore not trigger any function, unlike earbuds where I try to wiggle it and hang up on someone. A mi me quedan grandes porque tengo un pie muy fino, así que las llevaré al zapatero para hacerle más agujeros.