Cassettes & Sprockets

What is the difference between a cassette and a sprocket? And what about calling them gears or cogs? And what about freewheels? The terms get somewhat interchanged within the bike industry, and it’s hecking confusing, but if you want to get accurate and pedantic, there’s a few distinguishing features that separate the terms.
A cog is a tooth on a cogwheel which connects directly to another cogwheel, like in a car transmission. Together they form a gear. They’re rarely found on a bike.
A sprocket is a “cogwheel” which connects via a chain or belt to another sprocket, so the design of the teeth is different as it’s meshing to a chain, not directly to another sprocket.
A cassette is just a collection of different sized sprockets, that with the help of a derailleur, allow the chain to move from one gear to another.
What’s the difference between cassettes and freewheels then? Well, where these differ is whether or not they have bearings and ratchets incorporated into their design or not. A cassette doesn’t have these, and relies on being attached onto a wheel with a “freehub” (which has the bearings and ratchets inside it) via a spline and lockring. A freewheel is a single sprocket or cassette of sprockets which essentially has that “freehub” built into it and threads directly onto a wheel designed to take such a thing. The cassette variety of these are common on very cheap bikes as they’re cheaper to manufacture, but don’t work as well and have mostly been replaced by the separate cassette and freehub design on modern bikes.
We stock a large range of cassettes, sprockets and freewheels from Shimano, Surly, White Industries and others.