Ear pads for on-ear headphones are generally made of foam. Memory foam pads that help customize fit are popular. Over-ear pads often have extra foam cushioning and are sometimes covered with leatherette or a suede-type fabric. Ear buds generally have tips made of plastic, rubber, silicone or foam.
Over time foam pads deteriorate with use and contact with dirt and sweat. It is often cheaper to buy replacement ear pads for worn or damaged ones than it is to buy a new set of headphones. If more than one person uses a set of headphones, it is more hygienic for each user if they have their own ear pads.
Check the manufacturer, model number of the headphones and dimensions of the ear pads before buying replacement pads. Follow guidelines in a model specific instruction manual for advice on how to change the ear pads.