The six inch pot is 6 inches wide at the top. It has a 1/8inch rim, making the actual top opening 5.75 inches. It is 5.5 inches tall and 4.5 inches at the base.
It is made of sturdy, translucent plastic that allows light to get to your orchid's roots. This is very helpful for most epiphytic orchids that are used to having their roots exposed in their native habitat (in trees). This would include Phalaenopsis, Cattleya, Dendrobium and many other. Phragmepedium, Paphiopedilums, being ground dwelling terrestrial orchids, should have opaque pots.