linear servos

I am looking at some big linear servos,price is right but can't
find documentation of how much force or "thrust" they are capable of.
Only specs are 20Hs,20Hn[assuming s,n mean south/north poles of
magnetic field]
Does anyone know the value of H ? and yes in spec sheet it is always
upper case.
Obviously I am interested in ftlb or Nm for calculating accel of
loads.

CB