Back to Putzmeister Technology Pumps Cells Free Flow Hydraulics S-Valve Hopper Backup Systems OneTouch™ Econo-Gear Technology: Hopper Our large capacity RS 907A hopper - the Big Mouth - handles 19.4 cu ft (550L) and incorporates a remixer, vibrator and splashguards. Its huge 9” (230mm) intake opening and 9” to 7” (230mm to 180mm) reduction prevents residual buildup and ensures quick, easy clean out.