For those who are interested, or looking to upgrade legacy surefire lights, Malkoff (I am not affiliated with the company in any way, but just picked up a couple of heads for my old Surefire 6Ps largely due to this thread) has their M61 heads marked down from $55 to $39 (boosts output from 65 to 325 lumens). If you sign up for their offers they'll email you a 15% off coupon. Free shipping on orders over $75.