I need a new chain & possibly a new cassette for my road bike. It's equiped with full Shimano Ultegra SL (10speed).

What the difference between Ultegra 6600 & Ultegra 6700?

Also, do I have to fit a Shimano chain?

> What the difference between Ultegra 6600 & Ultegra 6700?

100 😉
The 6700 is a bit lighter AFAIK. You don't have to use a Shimano chain.

kmc x9l chains are nice

kmc x9l chains are nice

Probably not very nice on a 10 speed setup.

As long as it's a 9 speed chain you can use any make.

As long as it's a 9 speed chain you can use any make.

But not on a 10 speed set cassette!

It's a 10 speed set-up, as per original post.

just put a SRAM PG1070 cassette and PC1090 chain on my road bike (replaced ultegra) and very nice it is too.

6700 has an aluminium carrier, I don't think 6600 does… but I could be wrong.
KMC X10 chains are great and I'd recommend one.

oops i read that wrong didn't i 😀

try and x10l 🙂

6700 is designed to work with the 6700 chain, which like Dura Ace 7900 is slightly differently profiled, they're directional too I believe, which is odd.

I'd stick with 6600, which still has an alu carrier and your choice of chain. I like the SRAM ones, but they're not particularly cheap.