HP LaserJet 4000/4050 Series Envelope FeederPart Number: C4122A Capacity: 75 Envelopes Envelope Sizes: Com 10, Monarch, DL, B5, and C5 Printing Speed: 12 envelopes per minute Compatible Printers: HP Laserjet 4000, 4000N, 4000T, 4000TN, 4050, 4050N, 4050TN