Prevent the dart and dart barrel lever loose , common metal dart bar Material:Polybutylene Quantity:50/100pcs Inner Diameter:2mm,Outer Diameter 4mm Color:Red,black,white Installation: Slip O-ring from the split end of shaft Anti-slip rubber ring for aluminium dart shafts Introduction: When you playing darts,darts are ebay to loose between aluminium shaft and barrel(plastic shaft doesn't have the problem).Anti-slip rubber rings could resolve the problem. Package includes: 50pcs or 100pcs rubber O-rings Notice: 1.1cm=10mm=0.39inch. 2.Please allow 1-2mm error due to manual measurement and make sure you do not mind before ordering. 3.Please understand that colors may exist chromatic aberration as the different placement of pictures.