Do not buy these, they are 99% a scam.  The Trezarcoin founder, ChekaZ, asked for them to show it working.  They shared the mining page with him, and it showed that hash was from MiningRigRentals.  ChekaZ contacted MiningRigRentals and they said that this was rented hash from someone that they knew, and this person who was renting the hash out was NOT from Bittech.