M3 for <4 contacts using single blocks in front mounting with integral LED
M6 for <2 contacts using single blocks in front mounting with integral LED and transformer
M10 for <2 contacts using single blocks in front mounting with integral LED
MF1 for <2 contacts using single blocks in front mounting with integral LED
MR1 for <2 contacts using single blocks in rear mounting with integral LED
M4 for <4 contacts using single and double blocks in front mounting with integral LED