From 2009 GOLF Magazine Buyer's Guide:
It's for: Better players
Dan Stone, VP of R&D, Titleist: "909D3 is designed to deliver a mid launch with low spin."
How it works: At 440cc, this one is the smallest of the bunch. It has the deepest face, the lowest CG and is the narrowest from face to rear. The 909 D3 is the easiest to manipulate shots with high or low, left or right. It also produces the least backspin and lowest ball flight. Company testing shows that the 909 D3 launches shots 1° lower with 300 to 500 rpm less spin than the 909 DComp. A curved sole, blindbore hosel and internal ribs all contribute to sweet feel and sound. You'll find it with the Titleist Aldila Voodoo (low to mid launch with lower spin) or Titleist Diamana Blue 65 shaft (tour preferred high launch with moderate spin).