See Section 300.15(E)
Integral Enclosure.
A wiring device with integral enclosure identified for the use, having brackets that securely fasten the device to walls or ceilings of conventional on-site frame construction, for use with nonmetallic-sheathed cable, shall be permitted in lieu of a box or conduit body.
FPN:See 334.30(C); 545.10; 550.15(I), 551.47(E), Exception No. 1; and 552.48(E), Exception No. 1.