Nursing moms are often afflicted with plugged ducts, engorgement or mastitis. Doctors and lactation consultants recommend cool or heat therapy to alleviate the discomfort associated with all these conditions, and to aid in milk letdown. Gerber Breast Therapy Packs work either hot or cold, are very effective, and I highly recommend them for nursing moms.
These are ring-shaped packs that are filled with a gel. They can be placed in the microwave for heat, and in the freezer for cold therapy. They stay warm and cold for a relatively long time (although you periodically do need to re-heat or re-chill them). Although they come in packs of two, I usually only needed one at a time, so while one was applied, I was either heating or chilling the other.
They are covered with a plastic that is textured like cloth, so they are soft and comfortable. They are not very thick, so can be slipped into a nursing bra (although they are very noticeable, so don't wear them around town!).
These make a great gift for nursing moms. I used mine all the time.