The gears on the rear wheel are called 'cogs' and when you put a few of them together in ascending size and attach them onto your back wheel, they are referred to as a 'cassette'. Most bikes built in the last few years have between 8 and 11 cogs in the cassette.
As of now we don't have weight details of Schnell Holts 009 29T. Once we get the update from the brand we will update the same on this page. Holts 009 (24 SPD) 29T