The 1634-440-AL-7 from RAF Electronic Hardware is a round threaded aluminum standoff with #4-40 thread, 0.313" (7.94 mm) in diameter, with a clear Iridite finish.
The 1634-440-SS from RAF Electronic Hardware is a threaded stainless steel round standoff with #4-40 thread, 3/16" diameter and 5/16" (0.313" / 7.94 mm) length.
The 1634T-440-AL from RAF Electronic Hardware is a round threaded #4-40 aluminum standoff with a plain finish, 0.344" (8.74 mm) in diameter and 11/32" long.
The 1634T-440-SS from RAF Electronic Hardware is a round threaded standoff with #4-40 thread, stainless steel construction, 0.344" (8.74 mm) diameter, and 11/32" length.
The 1634T-440-N from RAF Electronic Hardware is a round threaded standoff with #4-40 thread, nylon construction, 0.344" (8.74 mm) diameter, 11/32" length, and no finish.