... area,making tension test Tension force:custom. Item nameTennis ball with elastic string and computer stringMaterialPolyster/LatexDiameter0.45mm-0.5mm ColorBlack (we ... pantone color) Feature Eco-friendly,elasticShape Round Use Garment,tags,elastic ribbon. clothing, pants, hats, gloves, socks, fabric & other reflexible ... a opp,and many tube in a carton tennis ball with elastic string and computer string