Every one of the key fitting specifications in any set of irons, that’s what – the lofts, lies, shaft flex, shaft bend profile, shaft weight, total weight, headweight feel (swingweight or MOI), grip style and grip size. Not only that, but it is possible that some golfers could be more comfortable with a slightly different single length than other golfers. In short, even though the lengths of each iron will be the same, what that length should be as well as each one of the other key fitting specifications should be custom fit and custom built for each golfer.
Single length does NOT mean “one size fits all” in the manner of the way big golf companies sell their clubs in standard form, off the rack. Single length sets still need to be properly custom fit to each golfer based on their size, strength, athletic ability and swing characteristics for the best single length and lie along with the right shaft weight, shaft flex, shaft bend profile, swingweight/MOI, set makeup and grip size/style.