... test area,making tension test Tension force:custom. Item nameTennis ball with elastic string and computer stringMaterialPolyster/LatexDiameter0.45mm-0.5mm ColorBlack ... be return to you Core Material Rubber; Latex; Spandex, as per the client's request Rubber/Latex 23#,28#,32#,37#, ... tube,rubber straight tube, OEM/ODM acceptable Packing method 1 tube insert a opp,and many tube in a carton tennis ball with ...