Glass headed pins have a head made of glass, not plastic.
Because of the head made of glass they are heat resistent and even a runover with an iron is not a problem!
A plastic head can melt when in contact with an iron, then you get a stain in your fabric that won't come out. 

Glass head pins are standard pins, our number one seller! Great pins to start out with, then to extend your supplies
with thinner and longer pins by Clover or Prym.