... ,making tension test Tension force:custom. Item nameTennis ball with elastic string and computer stringMaterialPolyster/LatexDiameter0.45mm-0.5mm ColorBlack (we can ... , as per the client's request Rubber/Latex 23#,28#,32#,37#,42#,52#,63#,90#,100#, Spandex 420D, 560D, 840D ... /ODM acceptable Packing method 1 tube insert a opp,and many tube in a carton tennis ball with elastic string and computer string