All of these gems have silver flat back foil (non see through) except black that is opaque (full black covered). Perfect for jewelry making, fabric embellishments, garments, Costume making, cosplays, clothes and shoes. All of these gems have silver flat back foil (non see through) except black that is opaque (full black covered 25 Pieces of Flat Back Sew On Heart Acrylic (plastic) Rhinestones, Size: 20mm or about 3/4 Perfect for jewelry making, fabric embellishments, garments, Costume making, cosplays, clothes and shoes. Strass Coudre Allstarco 20mm Jet Black CH37 Flat Back Sew On Heart Dies Tattered Lace Make sure to check out our store Allstarco USA, we have over 2000 of beautiful acrylic gems in different sizes and shapes, from Tiny 1., 5mm up to HUGE 60mm. These jewels have 2 holes for sewing that are about 1mm in diamater. CPSIA and RoHS compliant.