US pumps and European pumps are generally not interchangeable because of the differing cycles in the electrical current. There are two ways around this: 1) Use a pump with a select feature to change the number of cycles per minute 2) Use a pump with a battery pack. Recharge the battery off European current with a regular adapter, then run the pump off the battery. Yes, the European bottles have a larger opening than the US bottles. AVENT makes an adapter so US pump kits can be adapted to European bottles (part #142). The company can be reached at 1-800-54-AVENT. Elizabeth Novelo Puzar, IBCLC San Jose, California, where it really is springtime...I've been reading about the never-ending winter in the Midwest, but I bet a three-bedroom two-bath starter home costs less than a quarter million