The 7400-B is Shimano's "aerodynamic", semi-oval, shaped Dura-Ace post. It's design and shape is a variation on the Deore AX seatpost released as a touring grouppo in the early 1980's. There are 5 major parts to the 7400-B post, the mast assembly, two clamp pieces, the fastening bolt and a steel spacer. The mast assembly is a true work of art. Machined of a single piece of billet aluminum, there is a great deal of intricate workmanship involved in its oval-aero shape. The interior of the mast is bored out to reduce the weight, leaving a 2.7mm wall thickness and sturdy top section to support the clamp pieces. The clamp pieces rest in a machined cradle that permits the clamp angle to rock and be cinched at different angles. A slot milled through this clamp support allows the fastening bolt to pass up through the bottom of the cradle into the upper clamp piece. The fastening bolt rises through a chrome steel spacer (the spacer has a 9 gram weight) located beneath the bottom of the clamp saddle. This spacer fits in a half-rounded hollow and has flat ends. At the front, near the top, there is a 3mm steel hex bolt which pushes or holds the spacer and the fastening bolt in a fixed position. This small bolt can permit tiny adjustments in this micro-adjusting seatpost. Setback measured at 19mm on a 73º seat tube. The fastening bolt is chromed steel with a 6mm hex head. It's 8mm by 1mm thread pitch with a 34mm length and a 17.5 gram weight. The clamp pieces are both cast of aluminum alloy. The upper clamp piece resembles the Ritchey and Campy upper pieces, having threads for the fastening bolt to grip and four points of saddle rail contact. Each side of both clamp pieces offer 1 5/8" of rail contact. The lower clamp piece is cast with a hole for the threaded bolt anchor from the upper piece to pass into, as a "key" locking the pieces in place. There are knurles on the lower side which grip against the top of the clamp saddle on the mast when tightened. The entire post has a satin polished finish, with the name, in Black, etched on edge in the front. With the clamp perpendicular to the mast section, the center of rail to end of tube length is 200mm. The weight of a 27.2mm 7400-B post is 261 grams. The Shimano SP-7400-B Dura-Ace post is made in Japan, and is available in, 26.2mm, 26.4mm, 26.6mm, 26.8mm, 27.0mm, and 27.2mm sizes.

Shimano's top of the line race quality component group in the mid 80's through the early 90's. The 7400 series Dura-Ace group saw several interations including the introduction of 6 then 7 and finally 8 speed SIS shifting. Eventually upgraded with 7410 parts before finally being completely replaced with 7700.

Dura-Ace was developed to give the professional racing cyclist a fraction-of-a-second advantage that can spell the difference between victory and defeat. Advanced functions like 8 speed SIS, Super SLR brakes and Shimano Total Integration provide the most refined feeling of control available in a group today. Ultra high-precision mechanisms, quality materials and rugged construction assure that Dura-Ace takes all the punishment that pro-level road racing can dish out. (1991 Dealer Manual).