What is a roller chain offset link?
Offset links are used to add a "half link" to a strand of roller chain. Any strand of roller chain without the use of an offset will only have an even number of links. If your chain is a half link short, then you will require the use of an offset link. This links are primarily used on drives that have shorter lengths of chain where tensioners or adjusters are not used.
Downfall Of Using Offset Links
Offset links are actually weak link that significantly impacts the overall strength of the chain. Drives with low speeds and low loads may not be impacted with the use of an offset. If possible, you want design your application so it does not require the use of an offset.