Slubs, the irregular nubs in woven silk, were once considered a defect in the weave. In neckties, they are now considered an asset, adding as they do texture to ties woven from either shantung or tussah silk, two silks produced using different techniques to achieve a similar end.
Texture of course is one of the things that distinguishes a great tie from an ordinary one, and to my mind slubs are a prerequisite for a great summer tie.
There are half a dozen unlined shantung and tussah neckties with hand-rolled tips on the ASW store this weekend, including the new arrival in the photograph. Try using one to add character to a tropical weight worsted jacket.