The Arione Wing Flex CX K:ium is built with the essential trait of the standard Arione: Wing Flex technology. If you look at the rearward wings of the Arione CX K:ium, youll see that they flex to allow for free thigh movement. Your thighs wont get pinched by the saddle wings with the downward force of your pedaling stroke. This flex -- known as Wing Flex -- gives you a near-custom fit without sacrificing the critical shell rigidity & support you need for optimal power transfer & comfort. CX means one thing, it uses a lighter weight foam as compared to the non-CX version. This results in about 40g of weight savings & a slightly lower profile overall. Formerly, the Arione Wing Flex CX was available only in braided carbon rails. But Fizik now makes it available with K:ium rails. K:ium offers an 8% weight reduction compared to Titanium rails, & thanks to its use of Silicium & Chrome, it has better vibration-absorption qualities & more corrosion resistance. These saddles are ICS-compatible.