... ,making tension test Tension force:custom. Item nameTennis ball with elastic string and computer stringMaterialPolyster/LatexDiameter0.45mm-0.5mm ColorBlack (we can ... /2, 40/3, 50/1, 50/2, 50/3 etc Nylon 70D,100D,140D,170D,210D,420D,840D latex 52# Model ... /ODM acceptable Packing method 1 tube insert a opp,and many tube in a carton tennis ball with elastic string and computer string