Single-barreled sleeves are perfect for crimping over wire and monofilament to create your own leaders to use when fishing for toothy critters. The copper sleeves have a smooth, burr-free finish that won't damage your line. These sleeves hold tight and stand up to the rigors of saltwater battles. Per 100. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Leader Sleeves.