The anchor chain should be ordered along with your choice of plain or diamond discs.
The anchor chain is made from solid yellow or rose gold, and comes in two different lengths. 45cm or 50cm.
45cm is the standard chain length, and will be perfect with either 1 or 2 discs.
I usually wear my Y and H on the 45cm chain in the 15mm size, and layer it with a J in 20mm on a 50cm length.