I made the mistake (LOL) of looking at the Shimano Compatibility Charts. Until today I did not know these existed. However, looking at them only made me more confused.

I have two 10 speed chains on hand and Sram PG-1070 and a Ultegra 6600. Both 10 speed.

Now, if I am going to build a Space Horse with 10 speed GRX what 10 speed chain do I need?

So I consult the Shimano Compatibility Chart. I think it lists 7 or 8 chains - most begin with HG (so I assume hyperglide) and two that don't start with HG but if you look them up they are HG too.

So I suspect that rules out the 6600 Ultegra Chain since I think Hyperglide is MTB not road. I don't know if the PG-1070 is HG compatible.
now that

I am not sure that I improved my life by looking at the compatibility chart - I might have been happier with just installing one of the chains (probably the 1070) and calling it good. Now that I know these chart exist, I am going to feel compelled to look at them - perhaps ignorance is bliss.

So is either of the chains I have - perhaps the SRAM 1070 hyperglide compatible? Or do I just spend 25 bucks for a HG chain and sit the two chain I have back on the storage shelf? LOL

CN-HG is road (and gravel) too. They don’t differentiate.

That SRAM chain will be fine too but it doesn’t have quite the same miracle etchings as the hyperglide ones so you might find shifting not quite as slick. Or you might not notice.

Did they make 10sp GRX? I thought it started at 11 but probably not been paying attention.

Any of the Shimano or Sram 10 speed chains will work fine. Price difference usually means the cheaper chain is heavier, but IME, does not affect the performance. I usually go with what I find on sale, FSA, KMC, Sram, Shimano are all good.

With the Sram flattop chains, all chains conform to the same dimensional standards.

So pitch is always 1/2", rollers the same diameter, and width varies with the number of speeds (cassette sprocket separation).

There are differences in the shapes of the plates, but the effect of that I add subtle (if at all).

^^^^^

this

the 6600 (and 6700, 6701 etc) chains might be ‘optimized’ for road - and CN-HG95 might be ‘optimized’ for off-road - but all should work well

the SRAM 1070 chain should also work well

I use a CN-HG95 on my Shimano 10 speed gravel bike drivetrain … CN-HG95 is supposed to have ‘Sil-Tec’ coating which might be preferred for off-road use especially (?)

Like most people, you only really need to look at the number of speeds designation which relates to width. I always buy what's on sale at the time in the speed I need. If you tune your DR's correctly you won't notice a difference in my opinion.

I normally buy a mid-level chain at a good price ... KMC, SRAM or sometime Shimano (but generally no quick link but will still buy and the right price.) Then pretty much just match the number of speeds and installed.
But today I "discovered" the compatibility chart ... now I can really obsess about matching components ... When it comes to bike tech I can spend hours look and planning a build or upgrade or just watching videos of testing of bikes and bike components ...
Like tonight at dinner I subjected my wife to 3 YouTube videos on selecting the correct gravel tire ...

Thanks, I will install one of the ones I have probably the 1070 and call it good!

Now back to researching gravel tires ... I used to be a fun and interesting person!

I've been married for almost 45 years now and even I would never subject my dear wife to that kind of abuse. Tread carefully my friend

Shimano's compatibility chart only lists the 'current' and more recent models of parts that should be compatible. Parts from a few generations ago aren't listed. The 6600 was out in 2005.

The 6700 is a 'newer' version and had some changes (asymmetrical and beveled). Does that really matter? Enough to care?

The OP may be looking at the GRX 400 parts. Similar to the 4700 Tiagra series, RD is like a 11 speed for actuation ratio.