These jump rings are what I always use for any type of connector because they are strong for their size. For example, use them to connect chain to a clasp, or to connect a clasp to a foldover crimp.
They are also perfect for certain chain maille weaves, such as my
Chain Maille Project #123 - Japanese Chain Maille Necklace with Delicate Points.
4.5mm. outer diameter, 3.2mm. inner diameter, 20-gauge.
Price shown is for a bag of 50 rings.

NOTE: Some of the photos may make the rings look like they're not 100% round, but they are!