5/16"-18 x 1/2" x 1-3/4" Zinc Rod Coupling Nuts (8 pcs.)

Diameter: 5/16"
Diameter 2: 1/2"
Length: 1-3/4"
Material: Steel
Finish: Zinc
Driver Type: 1/2" Wrench
Thread Size: 18 (Coarse)
Style: Hex
Type: Coupling Nut

Box of 8.

A coupling nut is a long nut tapped from each side to meet in the middle, rather than all the way through in the same direction, used to connect two threaded rods end to end.