These ornaments are made of poly-resin, which feels like ceramic but it is much less breakable.
Size: varies from approx 4x5" depending on how big the family size is.
Decoration with vinyl can be a challenge. Last year, some used waterslide, other's freehanded with oil-based sharpies last year. Do what works best for you, or sell them blank.
Some ornaments are made with glitter and the glitter is expected to shed somewhat (just like last year) during transit and will come off when you prep the surface for vinyl/paint pen.