The Continental Race Light road tube is approximately 20 grams lighter than the standard Continental Race tube. It is a quick and low-cost way to reduce rotating weight. They tend to be slightly less puncture resistant than a standard weight tube but still very durable in the scope of tubes.
The Race Light is offered in several valve stem lengths. For standard rims and semi-aero rims like the Mavic Ksyrium choose 42mm. For deeper aero rims choose either the 60mm or 80mm valve stem. A good rule to select the correct valve stem length is to make sure it is at least as long as the profile of your rim plus 18-20mm. The valve core is removable so you can add sealant and are compatible with a variety of valve extenders.
LOVE these tubes. Takes a week for them to lose 5lbs. of pressure! I usually have to repump tires daily. Even though I still check these before every ride, rarely do they need air!