Why is there no 20 inches of gold rope chain?

Thank you for your question. The order of gold rope chain size is 18inch/22inch/24inch/20inch, 20inch is next to 24inch, you only need to slide the property "Item Display Length" to find the 20inch gold rope chain. Hope my reply can help you.

How do I know if this rope chain will fit through my pendant?

It does have a narrow lobster- claw style clasp, but it still barely fit through the loop for my pendant. ( I bought it for a longer silver chain for my sapphire pendant.)

what size should I get?

Thank you very much for your question. If want to wear it alone, we recommend the 16 or 18 inches for women, and 20 inches for men. If you want to add a pendant to it, we might be more likely to recommend 20in. But the length choice is depend on individuals. Hope this helps.

Any 16 inch available?

Thank you very much for your support of "Jewlpire". We are so sorry that currently it's not available. Could you please contact us through clicking "Sold by Jewlpire" on the product detail page or your Amazon order page and you will be directed to "Ask a question" to send us message. So that we can message you once the 16 inch silver rope chain is available. Hope this helps.