The Avent Manual Breast Pump is a manual breast pump with 4 ounce bottles. The pump is designed to physiologically stimulate a natural milk flow most like natural breastfeeding. It is the only manual pump with a gentle let-down massage cushion that flexes as you pump and creates a reliable vacuum, so you can extract milk gently and quickly. The Avent SCF310/20 is clinically proven to be as effective as competitor electric pumps, resulting in the same amount of milk in the same amount of time and also rated by mothers as more comfortable to use. The Avent SCF310/20 works with the entire AVENT natural feeding system and lets you pump, store and feed in any bottle or cup.