These pre-sterilised original Spectra Milk Storage Bags are very easy to connect to your breast pump.  They are treated and coated specifically to block out moisture and air, keeping the expressed milk fresh.  They can be sealed tightly to avoid contamination or leakage and the scale on the front of the bags lets you see how much milk has been expressed.  These bags are double-walled and freezer safe, and come in a pack of 30.