You can knit this pattern either with doubleknit wool and needles Size 2.5 mm, or four-ply wool and 2.0 mm needles.
I have mine as a decoration in my bathroom.
If you knit one-piece you can make a curved shell, which you could use as a small dish.
Two shells sewn together will make a small toy. Or you could put lavender inside to use as a clothes freshener.
My pattern explains how to knit either the plain or striped version.
And if you would like some shells already knitted up, then visit my Etsy shop at https://www.etsy.com/shop/GinxCraft where I have some sets of seaside creatures for sale.