Plastic screw caps come as either ribbed or smooth, child resistant or tamper evident.  They vary in sizes and lining varieties ie. foam, pressure sensitive or heat seal lings.  Some even come with a double lining for added security after the bottle is opened.  They range in sizes from 15mm to 120mm and usually come in white, but black may also be available upon request.  Custom colors are done upon manufactuters requirements.

Metal screw caps are primarily for f-style tin cans and come in 1", 1 1/4", 1 3/4" sizes with either Solvseal or Foil lining.  They may be regular screw cap or Child Resistant cap.