Though, our test Serano RXL in 138mm did come in 4g lighter than claimed, so there’s that. The black saddle was an early sample, while the white saddle that just showed up is 6g less. The Serano RLs on the bottom row range from 225g, to 237g – interestingly, it’s the middle sized, 138mm saddle that is the lightest. Claimed weights for the Serano RL are 210, 215, and 220g (128, 138, and 148mm) and 180, 185, and 190g for the RXL.As it turns out, even with the 7g penalty for the oversized seatpost adapter, there is still around 43g difference between the RL and RXL. As Tyler has trained me to be one with my gram scale, the oversized rail adapters will add 7 grams to the post – which takes a small bite out of the RXL’s claimed 30g weight savings over the RL. These days, there is a lot that goes into the making of a new saddle platform. Rather than just simply designing a shape based on previous successes, saddle designers rely on medical science, elite rider testing, pressure mapping, high speed video, and even the use of FEA to see how human tissue will compress when seated on a saddle. Many saddle manufacturers have begun to incorporate pelvic width into selecting the proper sized saddle, but just as important is the selection of the right saddle for the rider’s posture. Bontrager breaks saddle usage down into five categories including Leisure, Fitness, Performance, Aggressive, and Aerodynamic. As you travel up the scale, saddles offer more curvature and more gradual transitions based on the seating position and rider posture.As the latest saddle platform in their “Aggressive” category, the all new Serano offers a classic shape, in a saddle that is anything but. UPDATED with weights of all three Serano RLs plus more information on saddle sizing. Other than the futuristic looking Zone Density padding, the Serano’s shape is that of a classic saddle with curvy lines and a slight scoop at the tail. In marketing speak Bontrager refers to that as the “power pocket” or Posture 2, but it allows for the rider to settle back into the saddle, rotate the hips forward, and push off the back of the saddle for more power. The horizontal curvature has little flat space accommodating a more aggressive, forward leaning position, and a narrow nose to keep the thighs from rubbing on the saddle. Seranos are 270mm long and either 128, 138, or 148mm wide.3Both the RL and RXL gain their lightweight support through a carbon reinforced shell – the difference between the two being the hollow Ti rails of the RL and oversized carbon fiber rails of the RXL.That of course means you need an oversized rail compatible seatpost if you’re going to run the RXL. Some posts are compatible with both round and oval rails, but if you’re running a Bontrager seatpost like the XXX model here, you will need the 7x10mm saddle clamp (part #421564). The adapter is simple to install, and then allows for the saddle to be clamped with a single bolt – just make sure to use a torque wrench for the sake of the carbon! As the saddle underneath Andy Schleck since the Tour of California, Andy continued to use the Serano RXL throughout the Tour de France while a number of his team mates were riding the Team Issue. Like the other saddles in the Bontrager range, the Serano RL and Serano RXL will be offered in three inForm BioDynamics sizes. Using the inForm saddle sizer, consumers can be fit to the particular size at their local Trek dealer. White and black microfiber covers are available in both the RL and RXL models, though the RXL gets a few upgraded details like the embroidered tag on the rear instead of the embossed version on the RL. Pricing is set at $149.99 for the RL, and the more expensive RXL going for $224.99. Sizing of the saddles is done at your local Trek dealer with the Bontrager inForm saddle sizer. The sizer uses a “Z-flo” compound (white goo) that is trapped in a clear, flexible vessel. Underneath is the position slider that is designed with one side for men and the other side for women. On each side you’ll find colors that match up with the saddle sizes. Placing the sizer about 14 inches off the ground on a hard level surface (most shops will have a special bench for this), you’ll sit on the sizer with your back straight, allowing your sit bones to press into the Z-Flo. After marking the center of each impression with your finger, the slider is moved until the center of the impressions lines up with one color – in my case, yellow for 138mm.First Impressions:As a fan of the classic shaped saddles, my perineum has had little trouble adjusting to the Serano RXL. Sitting upright on the saddle with your hands off the bar to eat feels a little uncomfortable, but as soon as you tuck back into the bars that feeling goes away. It seems the more aggressive your positioning on the Serano, the more comfortable it becomes. I could see potential issues with cutout devotees, though it’s still worth a try if you still haven’t found the right saddle – especially considering Bontrager’s 30 day comfort guarantee. Based on the aggressive curvature of the saddle, the Serano seems like one that is very important to be sized correctly. So far, the Serano seems to be a hit.