The 5000S and 5000US Series set screw couplings are used for grounding and securing EMT raceways together.
Appleton's ETP Steel EMT Set Screw Couplings Catalog Page
O-Z/Gedney's ETP Steel EMT Set Screw Couplings Catalog Page
5150US
Switch & Outlet Boxes and Covers
NEER EMT Steel Straps