BY FAR the DURABLE longest lasting NON-oring 219 chain. Proven durable and used by several E-bike manufacturers. Also used for Surron #219 conversions, etc. Panther chains DO NOT USE a traditional style master link. Chains are pre-assembled complete. Chain tool is required to adjust the length. FTP Adjustable Chain Tool recommended for wider heavy-duty #219 chains. We recommend Motul Factory Line Chain Lube for high torque applications. If it attracts too much dirt on offroad applications, use Motul OFFROAD Chain Lube. Number of links = OUTER PLATES x 2. Specify links for CUSTOM length in CUSTOMER NOTES at checkout.