Incorporated in the State of Illinois under a Charter issued July 11, 1952 Plastic Capacitors, Inc., has remained a privately held corporation. Its history has included a steady record of expansion, research and product reliability. Employing about 100 people, it is classified as a "Small Business" by U.S. Government definitions. Due to its manageable size, it is usually more responsive to special customer requirements that large firms might be.

P.C.I. product lines are a combination of off-the-shelf and special High Voltage products. About half of sales are represented by custom designed items that are not contained in this Web Site. Capacitors for 250KV RMS 60MZ powerline use or high frequency AC; power supplies for X-ray CAT scanners, lasers and electrostatic coating; are examples of commonplace production at P.C.I.

For many years, the headquarters for Plastic Capacitors, Inc. was located on the northwest side of Chicago. In 2014, P.C.I. was purchased by Electro Technik Industries. Inc. and moved into the Tucson, Arizona facility with its sister company Arizona Capacitors, Inc.