New chain - which one do I buy?

[soulful dog]

This might be a daft question but what chain do I need as a replacement on my Dawes Horizon (24speed)? 

I thought it'd be an 8 speed chain but I see the new Horizon listed as having a Shimano HG40 chain, and found it on CRC, but it's a 7 speed?

 

[Cheule]

I've just replaced the chain on my 24 speed with an SRAM PC-850. So far so good

A breeze to install

 

[Mark_Robson]

I may be wrong but I don't think that there is any difference in size between a 7 and 8 speed chain. My road bike has an 8 speed cassette and I replaced the chain with a 9 speed chain purely to reduce the amount of trimming that was required and it's fine.