Most grey velvet decorative covers use hidden (concealed) zippers; some finished cushions or pillow inserts are made with sewn seams (no zipper closure).
Thickness varies by product but many 20x20 velvet throw pillows fall in a medium-to-firm range; product descriptions commonly list around 5 inches for some inserts and a 6–8 inch loft for plusher, shape-retaining options.
You can buy grey velvet pillows as single pieces or as multi-piece sets; examples include individual 20x20 throw pillows and complete 4-piece bedroom pillow sets that come with inserts included.
Some velvet decorative pillows are OEKO-TEX Standard 100 certified, indicating the pillow components were tested for harmful substances.
Listings report both polyester-based velvet (for example, 80% polyester velvet) and heavyweight 100% cotton velvet constructions for the face and back.