This is the Associated package of two 4-40 turnbuckles. These turnbuckles are constructed of black steel. They are 2.620 long with a square-shaped piece in the middle, which when turned by a wrench makes the linkage assembly lengthen or shorten (the threaded portions are reverse threaded on one side).
Two 4-40 truck turnbuckles
Ball cups, suggest ASCC2374