These premium 1X Sram Direct mount BOOST148 compatible Oval chainrings are designed for GXPÃÂ® and Long BB30 spindle cranks. Chainring is dedicated for Boost148 bikes ONLY. Converts a regular Sram crank into a Boost specific setup. Size (Mass +/-1g): 28T (50g), 30T (55g), 32T (59g), 34T(66g) Compatibility SRAM XX1, X01, X1, X0, X9, X7, S2210, S1400 and Truvativ AKA cranks. GXPÃÂ® and Long spindle BB30. BOOST148 bikes ONLY Material CNC machined 7075 Txxx Aluminium. Long-lasting construction. Finish Type II anodizing Chainline 52mm BOOST148 specific chainline Ovality Optimized to each size separately. Range: 10.2-14.4% and Timing of 110.5-116.3ÃÂ° after TDC (top dead center) Patent Pending This oval chainring with special 3mm offset converts any Sram crank into Boost148 specific setup needed in Boost equipped bikes. Boost and non-Boost Sram cranks are identical. All the offset is achieved by the chainring itself, so you can use any Sram crank for this conversion. Our regular GXP OVAL chainrings have 6mm offset whether this one has 3mm, but both chainrings look very similar. Advantages of our special Direct mount Boost chainrings: *Finest design to provide excellent weight to strength ratio *One of a kind special oval shape (Patent Pending) *Greatly improves traction and climbing abilities *Unique Patent Pending Narrow Wide tooth profile to keep your chain in place for minimum 12 months! *Special 3D teeth machining for ultimate mud relief decrease wear and noise dramatically *They save weight because they don't need the spider and chainring bolts. *The ability of installation of a smaller ring sizes that can't be mounted on regular spider. *Superb quality and great look. *You will ride faster using ovals. If you keep using round ring then others will get quicker. *You will not "feel" the oval shape at all *Reduces stress on knees *We mastered our oval chainrings to perfection, so you can get best possible advantage from the oval/elliptical shape. Why our oval chainrings work Our Oval chainrings work because a rider does not produce power evenly through a pedal stroke; they maximize the part of the stroke where power is produced and minimize resistance where it isn't. Oval rings make the spin cycle a lot smoother and are easier on legs while climbing. Believe it (or not), but a round chainring doesn't transfer torque to your rear wheel as smoothly as an Oval one. You will actually feel your stroke to be more "round" with an Oval shape than with a round chainring. Why it matters Traction, Traction and Traction. With oval rings rear tire traction improves greatly on loose and slippery terrain. Smoother power delivery to your rear wheel means that you will be able to maintain better, constant cadence; get less stress on the joints (knees) and therefore be able to keep certain level of effort for longer. This results in higher average speed. Moreover, 11 studies made by various Universities in the World show that using oval chainrings human legs utilize more muscle groups (compared to round one), but each of them to lesser degree. Load from pedaling an oval chainring is spread over greater muscle mass which in effect gives you the feeling of fresher and more relaxed legs. It is world's finest oval chainring backed by tens of thousands of customers. What size should I choose? * 28T Oval chainring has an ovality of 26/30T and is best for someone who uses currently 27 or 28T round ring. * 30T Oval chainring has an ovality of 28/32T and is best for someone who uses currently 29 or 30T round ring. * 32T oval ring will suit best someone who uses 31 or 32T chainring currently. While pedaling, you will feel similar effort to the one riding round 31T ring, but you will gain the speed similar to riding 34T chainring. * 34T Oval chainring has an ovality of 32/36T and is best for someone who uses currently 33 or 34T round ring.