Advice on slimmer belts

Hi, I wanted to know everyones advice on slimmer belts as I came across them in a sports shop. The slimmer belts such as Everlast etc. Are they any good and effective? I thought about wearing one for when I'm on long walks or on the cross trainer. Does anyone else have one and what brand is the best? I've noticed that the Everlast is the most popular one but I want other peoples opinions before I start buying one or if it's worth buying.