Ptera SY | Size 10As all good things come in twos the Ptera SY linked ring thrives in its two heavy gauge band design. Focused on boasting the rich and bold tones of . 925 sterling silver as well 18k yellow and rose gold, the Ptera SY linked ring functions perfectly with other stackable Spinelli Kilcollin rings, or on its own as a statement piece. Each Ptera SY linked ring is handmade in Los Angeles. Bands: 18k yellow and white gold 3. 8mm gauge 18k white gold band 3.