This straps cause high stress on the spell caster's body.

Zahyr's straps allows its user to maintain concentration in more than 1 spell at a time. To do so the caster must succeed on a constituion saving throw  DC 10 + total level of spells being concentrated. You lose all spells concentration of a failed check. Alternatively Zahyr's straps allow the user to cast a second concentration spell with a modified duration of one turn without penalty.