I'm often asked about 'which chain suits x pendant' etc, so I figured I'd create a small write up to help you make a decision on which chain is best suited for your needs.
First step, choose which of the 3 types of chain you prefer. As of the time of writing this blog post, I currently have a 1.7mm belcher, 2.5mm belcher and a 3mm cable chain on the shop.
Also, just to clarify: the 'mm' measurement is the chain's width, the 'inch' measurement is how long the chain will be when worn.
In terms of thickness, the 1.7mm belcher is by far the thinnest. The 2.5mm belcher and the 3mm cable aren't too different. The main thing is that all of these chains are suited to any of my pendants, though I'd personally suggest a 2.5mm belcher if you're unsure, it's a great middle-ground for the tiny pendants but also and the biggest pendants I have on the shop (it's also the chain worn by Frodo on his journey to middle-earth so you clearly can't go wrong there).
Once you're happy with the chain design choice, it's time to start thinking about the drop/length of the chain. The most common length is 20'' - it's not too short so it'll sit too close to your collar, and it's not too long that it'll have a lot of movement. Ultimately, it's just preference. Choose a length you're comfortable with. Every pendant I make is compatible with all 3 of these chains.
Hope this little guide has made your choice a bit easier, feel free to drop me an email if you'd like further help!