Balancing aerodynamics, weight, and affordability, the new ULTEGRA R8170 C50 wheelset is sure to inspire action on your group ride with its all-new tubeless carbon rim and updated, 11 and 12-speed compatible hub.Summiting climbs, carving descents, or cruising the flats, the new C50 is the jack of all trades among the new ULTEGRA R8170 wheel lineup. The tubeless, carbon rim features a 21 mm internal width that pairs nicely with wider, modern tires while the HYPERGLIDE cassette body is compatible with 11 and 12-speed cassettes.Features:- 50 mm height full carbon rim- Internal rim width: 21 mm- Shared rim profile with R9200 DURA-ACE wheelsSpecifications:- Average weight: 698- Spokes_Straight pull: Yes- Brake type: CENTER LOCK disc brake- Axle fixing method: 12 mm E-THRU- Internal grease sleeve: Yes- O.L.D. (mm): 100- Thru axle (length x inner diameter , mm)_100 x 12: Yes- D2 rim: Yes- Disc mount_140 mm Disc brake rotor compatible: Yes- Disc mount_CENTER LOCK: Yes- Front/Rear: Front- Reflector_AS: CATEYE RR-550-WUW SW- Reflector_DIN: CATEYE RR-317-WUA SW- Reflector_JIS/CPSC: CATEYE RR-550-WUW SW- Rim_Height (mm): 50- Rim_Requires rim tape: Yes- Seal_Hub: Contact- Spokes_Bladed: Yes- Spokes_Butted: Yes- Spokes_Number: 24- Tire_Recommended size: 25-622 - 32-622- Tire_Type: Tubeless- Wheel Size: 622 x 21C- Model name: WH-R8170-C50-TL- Rim_External width (mm): 28- Rim_Internal width (mm): 21- Spokes_Diameter (mm): 2.0-1.6-2.0Technologies:D2:- Aerodynamic performance is affected by wind direction. To create the D2 rim, SHIMANO engineers considered both frontal and cross winds, aiming to achieve optimal performance in real-world riding conditions. Extensive prototype testing, in the wind-tunnel and on the road, proved that a wide rim shape with a deep tire bed performs best across a wide range of conditions. At yaw angles ranging from 0 to 15 degrees, the SHIMANO D2 rim profile reduces air drag better than others aero shape rims. This rim design also boosts lateral wheel stiffness and offers improved vertical compliance for increased control, comfort and durability on the road.OPTBAL:- The OPTBAL rear wheel spoke system features 21 spokes—14 on the drive side and 7 on the non-drive side. Cassette spacing in today's wheels produces unbalanced tension in traditional 1:1 spoke systems. This unbalance is intensified with the 11-speed cassette, producing nearly double the tension on the drive side spokes. Generally high and low tension spokes have respectively tendency toward breaking down and coming loose spoke nipples. Unbalanced tension affects durability and strength.