We love these eco friendly, natural sisal soap bags. They fit most soap bars - measuring 3 1/2 by 5 1/2 inches - and have a drawstring to keep your soaps snug. Some soaps may discolour the bag (ie. charcoal soaps, beetroot, etc.) but they are washable and reusable.  I would suggest a wash between soap changes anyway.

Natural sisal bags add a nice exfoliating touch, especially when paired with a natural, hand made soap.

And the beauty of them is that you can hang them from the faucet to dry between uses.  They are also great to put all the little left over Soap ends in to get the maximum use out of all your bars.