Amazon’s Prime Day sales event starts Tuesday, but some shoppers have been browsing deals for weeks — hoping to snag an invite-only discount. Part of an ever-expanding Prime Day, Amazon rolled out a new, invitation-only deals program ahead of this year’s sale. The program allows customers to request an invitation to purchase discounted items that Amazon expects might sell out, including things like a Fire TV or noise-canceling headphones. There are a limited number of products available through the invitations, Amazon says, and once an invitation is in hand, customers have until the end of the two-day sales event to make the purchase, a spokesperson said. The invitations have been available for browsing for the last three weeks, Amazon said.