There's no limit to the design varieties of acrylic grinders, all colours and many shapes are possible. Very popular are spherical grinders looking like golf or billard balls.
Acrylic grinders - the right choice for smokers on a budgetThese plastic mills are made for occasional users with a strong sense for budget deals. Some acrylic grinders are available for just a few bucks, but do not expect them to be a lifetime companion.
Their cutting teeth are made from acrylic too and, therefore, are rather vulnerable to damage. Acrylic herb grinders are not made for eternity and don't provide the best grinding results. But, they will do their job well enough for occasional herb grinding.