Abstract: Assembly of sports equipment fillable with liquid and a gel-forming means, and sports equipment for use in this assembly. Article of sports equipment fillable with liquid such as a punch-bag. A punch-bag which comes from the factory ready for use takes up much space, is relatively heavy and is easily damaged in handling during transport. According to the invention the punch-bag is supplied to the user as assembly of the empty punch-bag (1) and a gel-forming means. The punch-bag (1) can then be supplied in empty state (small volume, low weight). After purchase the user can fill the punch-bag with water, to which the gel-forming means is added so that the punch-bag acquires the desired striking properties, in particular sloshing of the water during use is prevented in this way.