From Bra Maker's Supply:
The ever-so-popular Ruby bra pattern has another sister, the Amethyst lace Bra Pattern. The Amethyst like the Ruby, is a full band bra, so it can be worn with or without wires. Like the Ruby, this pattern features an off-set vertical seamed cup for the roundest styling, and a shortened upper cup for maximum lift. Our testers were amazed at the push-up look this pattern gives. The Amethyst Lace Bra Pattern has been specially designed to use with foam lining, therefore enabling you to use virtually any stretch fabric over it as a cup cover. But it can even be made without foam, using low-stretch fabrics or fabrics lined with Sheer Cup Lining.
The Amethyst has a band made from lace edging, so the scallops of the lace actually follow the contour of the bottom edge. The centre front seam will allow you to mirror the lace perfectly on both sides of the frame. The lace edging is also used along the neckline of the upper cup where the scallops peek out over the foam lining. What’s more, the strap extension also sports lace edging, which makes the Amethyst the most lace-intensive bra pattern we’ve created.
One other thing about the Amethyst pattern. The cups and band are interchangeable with the Ruby pattern. That means if you love the lace edge upper cup of the Amethyst, but you prefer the plain band of the Ruby, you can use the Ruby band with the Amethyst cup. Likewise if you prefer the tailored look of the Ruby cup with fold-over binding along the neckline edge, but you love the lace band of the Amethyst, you can switch those up too.
The sizing for the Amethyst is a bit different from other bra patterns, in that we use the Bottom Cup Depth (BCD) to determine the size of the cup. This is the measurement from the wire line at the base of the cup up to the location of the apex. It is much more accurate than relying on Ready-to-wear bra sizing, which can differ from company to company. Determine your BCD by measuring your best fitting bra between these two points. All cup sizes from 3.0 to 6.0 are included in the pattern. Combine these 13 cup depths with 1 of 8 band sizes from 26″ (65 cm) through 40″ (100 cm) to make the Amethyst Lace Bra Pattern size range equivalent to over 100 unique bra sizes.