90 x 15 mm Petri Dish, with Safety Lock, Sterile, 20/pk, 500/cs. These non-treated polystyrene plates are transparent and DNase/RNase-Free. The bottom has a ridge allowing for easy handling and stacking. The plate has three vents for gas exchange. • High clarity polystyrene• Flat, transparent surface• Stackable for easy storage and handling• Sterilized by E-Beam• Non-pyrogenic