Rollerfly is a set of 4 slide plates with ball bearings that attach to ice hockey goalie pads to allow for sliding, butterfly style movements on sport court, concrete, wood and more surfaces. They enhance movement and greatly reduce fatigue in the body to allow goalies a much better experience. Currently available in Black, with more White on the way. There are two types of replacement balls. The plastic balls are used on plastic tile, sportcourt, ice court, wood, etc and will wear down and can be replaced. The metal bearings are used for concrete or similar surface which will allow them to roll smoother and be more durable. 270 balls total are needed to replace a full set of Rollerfly Balls.