I advice to take a cosmetical grade, or lab grade internally. Just to be at the safe side.
- But if the Mule team box says "99,5-8 % sodium borate and no other ingredients listed, you should be safe with it.
The cosmetical grade is 99,9 "pure", so in practice there are little difference.
The boron used for boron supplements, are made from borax / sodium borate. Then the fillers comes in, as there are maximum 3 mg of boron in a capsule. Hardly visible, and no one wants to buy an almost empty capsule :)