517 crystalline phase" (5Mg(OH)₂·MgSO₄·7H₂O) 

517 is a very stable crystalline phase in MGO boards, formed by Mg(OH)₂ and MgSO₄ intertwined with H₂O to create a very stable crystal structure. It provides strength and weather resistance to the board.

For mgo board, since it is related to the chemical reaction, so if without the strict control, it is very easy to meet some inconsistency issues.
Some batches of products are good, some batches are not good. 

How to check the factory mgo board could have consistent quality? 

The scientific way to is to test the 517 structure. 

Our mgo board keeps doing the 517 test, then shares the result to customers, so that we can guarantee the consistency of mgo board. 

If you need the 517 report, pls kindly feel free to contact us.