Sodiummetaborate-tetrahydrate (x 4 H2O) and -octahydrate (x 8 H20) are in fact the same. The formula for the first is NaBO2 x 4 H2O and for the second Na2B2O4 x 8 H2O which is the double of the first. You can see a good data sheet on the website of 20 Mule Team Borax (www.borax.com). Also on the market is the dry (sicc.) version without crystal water, but "Kodalk" was the hydrate.