DCI 4438 - Automatic HP Quad Block w/Long Adjustment ScrewsHP Quad Block w Long Adjustment Screws Used on DCI Edge Series 4 5 Delivery Systems Used on DCI Edge Series 4 5 Delivery Systems Works with normally closed automatic Consistent flow control for handpiece pressure adjustments Higher output due to improved airflow Longer lasting diaphragm No internal cross over of air or water Twin Block dimensions, 1 1 2" x 1 1 2" x 1" Tri Block dimensions, 2 3 8" x 1 1 2" x 1" Quad Block dimensions, 3 1 8" x 1 1 2" x