Designation:

EM 20-20-501
EA 20 D
SA 20 C 

Construction:

The articulated head is a plain bearing housed in a housing with a stem for mounting. The rod of the articulating head is attached with an external thread.

Features:

Series E. 
External thread.
Low coefficient of friction.
Not to be used for complete revolutions.
For use in applications minimum axial loads and limited oscillating movements. 
Featuring a pressure-molded PTFE (Polytetrafluoroethylene also known as Teflon) sliding layer between the housing and inner ring, this combination of contact surfaces requires no maintenance or constant lubrication.