"SOLK" stands for, Single leg, Oblong master link & LK is a sliding choker hook.
These Grade 80 chain slings feature an oblong master link on one end, plus a sliding choker hook and a coupler to make the connection on the other end. The sliding choker hook connects to the coupler to make a safe and tight bite. Additionally, the flat profile of the coupler makes it easy to remove from under a load. These slings are very popular, for example, for picking rebar sections.