All male religious pilgrims making the pilgrimage to Mecca wear the same thing: a simple white outfit made of two plain pieces of cloth with no seams, buttons, or zippers. One is wrapped around the lower half of the body like a skirt, and the other is draped over the top part of the body as shown above. The fabric can be anything ranging from cotton sheeting to heavier fabric like a towel. All men dressing the same makes them all equal, no classes.
Women are not restricted in the clothing that they wear for the religious pilgrimage, but they must be covered properly according to Islamic standards, including the hair.