A backshell device and assembly are provided for achieved improved signal integrity, wherein the design of the backshell device is less complicated, more light weight, and easier to build and use than existing devices. In one embodiment, the backshell device can be coupled to adaptor which is coupled to a connector. The backshell device generally comprises a mounting section coupled to the adaptor, and an extension section extending from the mounting section. The extension section preferably comprises an increased-diameter section configured to accommodate a non-staggered or aligned arrangement of a plurality of solder sleeves of the wiring harness.