I took my r510 up to golfsmith to get a new grip put on it over the winter, and I ended up getting a free upgrade to a brand new r5 because my 510 had a dent in the face, and it was sent in as defective, and they even sent me one with a 757 speeder in it. the r5 is 450 cc I think, and i thought i would hate it, but i've never hit anything like this in my life, i added about 10 yards in driving distance and i'm hitting about two thirds of the fairways i see, as opposed to half at best with my 510 and other drivers. it is so forgiving on off-center hits and goes for days if you hit the sweet spot. i had a 5 iron in, about 205 yards, on a 550 yard level ground par 5 the other day.