Halco Aluminium Single Crimp Sleeve – 20 per packet Constructed with marine grade aluminium alloy, the Halco Aluminium Single Crimp Sleeve is a flat oval shape for easy collapse and comes in a range of sizes, with 20 pieces per packet. These crimp sleeves are resistant to corrosion and highly durable, making an excellent choice for serious anglers. These aluminium single crimp sleeves are ideal for joining monofilament line.