I am new to using an alum block. I picked up a no name alum block from an international market a few weeks ago. I paid less than $2 for a block about 1.5 inches square by about .75" thick. This weekend I was in a store that sells e-shave products and had an e-shave alum block for $20. It was probably about 2x the size of mine but it makes me wonder: Do all alum blocks have the same ingredients? Are some better than others?