Basically to top off the treasury as mentioned below :

Keith Neumeyer, President and CEO of First Majestic comments, "We are pleased to have entered into this agreement to forward sell a portion of our base metal production from both our Del Toro and La Parrilla silver mines. Management considers this arrangement to be very favorable at current market prices and it allows our treasury to be topped up without having to dilute our shareholders. Furthermore, First Majestic remains committed to being un-hedged on its silver production in anticipation of higher silver prices in the future, while only forward selling a minor portion of our lead and zinc base metals."