A rugby shirt is a shirt worn by players of rugby union or rugby league. It usually has short sleeves, though long sleeves are common as well. Rugby shirts have a buttoned opening at the top, in a similar style to polo shirts but with a stiffer collar. Modern rugby shirts often have a very small collar so as to provide less material for a potential tackler to latch onto (even though such an action is illegal in a game). Due to the nature of the game, the fabric is generally strong, and traditionally rugby shirts have rubber buttons so that they would, if pulled on in a game, come undone rather than pop off.