I bought this because the standard one that came with my pump was, as I learned, too small for me and partly the reason it was so uncomfortable and unproductive to pump. I wish they would tell you these things in the instruction manual or something so you could have an idea of how to size yourself properly for optimal comfort and flow. Overall this works OK, it is very easy to clean and sterilise and I'd recommend it if the standard size is a bit too small for you. However, after I discovered their softfit breastshield, which is comfortable for nipples of a large range of sizes, I soon chucked this. It is SO much softer and more comfortable and I no longer get horrible sores around my nipples from the hard plastic.