There are several different types of padding. The type we’ve been using most over the past few years is a product called rebound. It comes in several different weights. The heavier the weight the firmer the pad and the more expensive. Generally we use firmer pads under heavier carpets. Another type of pad we’ve used in apartments and basement areas is one we call fir pad. Its very firm, lasts a long time, and is relatively inexpensive. There are specialty pads like ones with arm and hammer in them for pet problem areas and one with a mildew reducer for damp areas to name a couple. Keep in mind when choosing a pad, your carpet tends to break down faster once the pad has broken down so always choose a pad that will last at least as long as the carpet your putting it under