0.5mm Silver Crimp Tubes for Elasticity. Inside Diameter 1.3mm. Outside Diameter 1.8mm. Length 4.0mm. Sold 80 pieces per pack. Crimp tubes for stretch cord are longer crimps made specifically to hold slippery stretch cord without knotting. Sized for the typical sizes of stretch cord, large medium and small. You can use crimping pliers for the strongest hold and most professional finish. For maximum security, add a small amount of bead stringing cement inside the crimp just before crimping.