KR521 Envelope Inserting System

Inserts products into large envelopes with ease.

Originally designed for the 9”x12” inserter market, the KR521 is flexible enough to handle most other sizes as well. From open end flaps, to long side flaps, even overnight letter envelopes, this engineering marvel is built to perform.

Using Kirk-Rudy’s highly reliable KR324 Shuttle Feeders to deliver inserts to the lugged transport belt, the KR521 delivers a consistent, smooth, and safe work flow. The envelope flap opening section utilizes a pinch roller/plow assembly combined with a compressed air blast to positively open every flap.

Like all Kirk-Rudy equipment, the KR521 is modular in design and is compatible with other Kirk-Rudy equipment such as turn-over units, labelers, inkjet printers, sorters, stackers and conveyors.


  • Heavy-duty, built for production environments
  • Add up to 9 inserting stations
  • Semi-automatic lubricating system
  • Handles up to 10”x13” envelopes, down to #10 size


Photo Gallery
See KR521 in Action