Medela's Easy Expression Bustier allows you to do other things while pumping. It's easy to wear and use, and can be worn on its own or over a nursing bra or camisole. Compatible with most electric breast pumps: Including Pump in Style, Freestyle, Symphony, Swing and Lactina to hold the breast shields securely in place while you pump. The comfortable cotton/spandex blend is machine washable, and available in black and white with sizes available that fits most moms. Authentic Medela spare parts are engineered, tested and approved to work specifically with your Medela breast pump. Non Medela spare parts can vary significantly in design, materials, and workmanship. All of which may affect the performance of your Medela breast pump.