Medium is steel.

Fitted with eight porcelain medium based sockets
Important: When used with shade use no more than 40 watts maximum (we suggest 25 watts)
Choice of patina is rust or black iron for most products unless otherwise specified.
We do not recommend using over 60 watt bulbs for any of the fixtures.
UL Listed dry locations
When applicable some chandeliers come with three feel of chain for a laced mount.   
Also included is a cover plate and mounting hardware.
Some of our chandelier products will require a reinforced junction box for the additional weight.
Please inquire if you have any concerns or questions about the weight appropriateness of fixtures.