Sram 10 Spd OG1090 Red/Black Cassette The main cogset of the OG 1090 cassette is machined out of a single forged form that is heat treated and then shaped in a complex series of CNC-guided operations. Weight, stiffness, and strength-wise, the OG 1090 Cassette delivers titanium's weight with solid steel's superior strength and stiffness. - Lightweight: Innovative CNC'd chromoly steel construction. - Durable: 35% harder than titanium! - Stiff: 15% stronger than its competitor. - OpenGlide technology allows for smoother transition between gears.