27770
Each rotor is a disc approximately in diameter made from Ebonite or Bakelite with 26 brass , spring-loaded , electrical contact pins arranged in a circle on one face , with the other face housing 26 corresponding electrical contacts in the form of circular plates .
 Ebonite, Bakelite
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Ebonite, Bakelite