... has several specification.They are SR4P2A1B22,SR4P2A1B24,SR4P2A1B24P,SR4P2A1B24N,SR4P3A1B24,SR4P2A1B24S,SR4P2A1Y,SR2P4A24The SR4P2A1B22 and SR4P2A1B24 are appropriate for E-stop Switch ... )It has removable terminals,facilitate installation and connection. Safety Relay SR4P2A1B24