tennis ball with elastic string and computer string it can use in computer test area,making tension test Tension force:custom. Item ... nameTennis ball with elastic string and computer stringMaterialPolyster/LatexDiameter0.45mm-0.5mm ColorBlack (we can do pantone ... , as per the client's request Rubber/Latex 23#,28#,32#,37#,42#,52#,63#,90#,100#, Spandex 420D, 560D, 840D ...