Acrylic tear drop shaped thread drops from 1/16" acrylic. Two sizes for thinner or thicker threads. You can write on these with a wet erasable pen which you'll find under Related Items.
For most cross-stitch and embroidery threads the 2" x 1.5" shape holds at least a full skein if not more. This size has 15 tear drops on the ring and the oblong hole is about 1" wide.
For most needlepoint threads that are heavier (e.g. tapestry wool) the 3" x 2.375" shape holds a skein. This size has 10 tear drops on the ring and the oblong hole is about 1.75" wide.
Both sizes are available in Clear, White, Red and Teal.