 Shares of Builders FirstSource Inc. BLDR, 0.08 rallied 0.7 in premarket trading Monday, after the building products and prefabricated components supplier boosted its stock repurchase program by 1 billion. The increase give the company authorization to buy back 1.5 billion worth of stock, which represents 16.8 of the companys market capitalization of 8.91 billion as of Fridays close. 