I was curious so, for fun, I weighed some myself (note the weight difference compared to Chuck's photos. I guess not all scales or pipes are equal).

In order: Mac's 6.5 MP (14.25", 3.3 oz), Hatori 401 7.5 (14.50", 3.4 oz), Mac's 7.5 QP (16.25", 3.7 oz).

In fairness to Mac's, the 401 is sized more closely to a 40 size pipe (6.5 cc) rather than a 45-50 size pipe (7.5 cc) even though its intended purpose might be different. The Mac's 7.5 cc QP is a much longer (and probably quieter) pipe although both the 6.5 and 7.5 share the same header OD of 3/4".

It appears that Hatori makes comparatively shorter pipes than Mac's for the same application. I was surprised when I purchased a Hatori 10 cc LS pipe (650) and saw that it looked more like a 7.5 cc pipe! I actually thought there might have been a mixup.

David.

P.S. Lorin, I'll drop you a PM in the next coupla days.