One form of exercise that users of gym equipment are interested in is, of course, weight training. Doing so requires the proper tools – such as a set of dumbbells. These are a type of gym equipment which gives the arm and shoulder muscles a good workout and increases strength. Currently, two kinds of dumbbells are in existence: the adjustable type – which appear as miniature barbells and generally measure 14 inches (one-inch diameter), along with weights up to 40 kilograms apiece; and fixed-weight dumbbells – which resemble the common dumbbell shape and are specifically measured.