Gemstone toggle clasps for jewelry making. These unusual gemstone findings have no metal, so are excellent for people with metal allergies! The toggle sets have an approximately 20 x 5.2mm ring, and 20 x 7.8 x 5.2mm bar, each with two large holes. Green Aventurine. Aventurine is commonly enhanced to bring out its natural beauty. Questions? E-mail us for friendly, expert help!