Formax FD 390 - Air Feed Commercial Document Folder [Full Warranty]. The FD 390 high speed document folder is ideal for mail rooms, print shops, mail houses or virtually any other high volume application. The bottom in-feed air system allows for continuous loading of forms while the extended out-feed stacker cuts down on the unloading of folded documents. Both features decrease processing time and increase efficiency. A chart for seven common fold settings is located on the out-feed stacker for easy setup. Microadjustment knobs are used to fine-tune the stopper position making crisp and accurate folds every time. Featured Highlights; Variable Speed: Up to 35,000 pieces/hrHeavy duty fold plates. Bottom air-feed system for continuous loading. Recommended Options: Cross fold in-line with the FD 396 Right-Angle Folder. Automatically square and align forms with a 402 Series Jogger.