My current set up chain and cassette has about 1000 miles on them. After measuring the chain (Dura-Ace) for wear it has stretched more than the recommended replacement stretch of 1/8". I was looking at the cassette (SRAM) and noticed the teeth appear to have a slight shark fin appearance but not much. Do cassettes come with the teeth shaped like this to allow the chain to better contact the rings or am I noticing wear. I am just trying to figure out if I need to be replacing the chain and the cassette or just the chain. I feel that 1000 miles on the cassette is not that much and have taken good care of the chain with lubrication and cleaning but it just has not held up well.

Hmmm... You might want to re-measure the chain. 1000 miles is far too soon for a chain to have that much wear, and far, far too soon for a cassette. Are you sure everything was new 1000 miles ago?

Measurements are correct, as for the exact mileage....I bought the bike used and the person I got it from told me that was the approx milage on the chain and cassette. Call me naive for listening to that but that is the only information that I have to go off of. I have no problem replacing the chain but if it can be avoided I was going to try to not replace the cassette. Either way when all is new I will know the exact mileage/care for the components and care for them accordingly.

my solution:

buy a new chain and run it. If you have problems w/ the cassette, then replace it.

Hmmm... You might want to re-measure the chain. 1000 miles is far too soon for a chain to have that much wear, and far, far too soon for a cassette. Are you sure everything was new 1000 miles ago?

maybe someone is severely cross chaining to cause wear fast.

That shark-fin shape is not normal. It indicates wear. Your chain is severely worn if it's stretched over 1/8" in 12". The worn chain has accelerated cog wear. As bop advises, get a new chain and see how it works. There's a high likelihood that it will skip under load on the most worn cogs, and you'll have to replace the cassette. When you get the new stuff, clean and lube regularly, and replace the chain when it shows about half the wear you see now.

When taking a close look at their cassette cogs, many people discover something that resembles a shark fin. But if your shark fins look like the ones in the photo, they're ramps milled into the cogs to make shifting easier and smoother, especially if the shift is made under power. Perfectly normal, and no indication of wear.

A shark fin formed by long-time wear has a sharp, undercut point at the very tip of a tooth.

I've built Sram Force bikes combined with Dura-ace cassetttes. I can't tell a difference between a Sram Cassette and a Dura-Ace one. They both shift smooth as silk to me.
Dura-Ace is about 2 ounces lighter however if you can afford more than double the price.

Matt P.