Power transmission chains and sprockets work together to transmit power between rotational shafts, providing a more precise and controlled drive system over belts and pulleys because they will not slip or wear. Roller chains consist of a strand of overlapping links with intersecting rollers that engage with the teeth of a compatible sprocket. Roller chain links and connectors are individual links that are added to an existing chain to replace a worn link or to extend the length of the chain. Roller chain sprockets and idlers have a series of teeth around a central bore, or hole, that engage with roller chains. Chain tools consist of manual devices that detach or join a roller chain so that it can be repaired or adjusted to a different size.