Pimlico Race Course will again offer infield patrons at the Preakness Stakes a $20 beer mug that can be refilled unlimited times, the company said on Tuesday when announcing that infield tickets had gone on sale. The $20 bottomless beer mug was first offered last year to reverse a 30-percent decline in attendance at the Preakness in 2009 after the track prohibited patrons from bringing their own beer into the infield for the first time. The bottomless mug offer worked: Attendance at the 2010 event jumped 23 percent to 95,760. Tickets to the infield can be purchased for $40 until the Monday just before the May 21 Preakness Stakes, when the price will increase to $50, according to Pimlico. The bottomless mug is an additional $20 over the ticket price.