1) The slot type (T or C slot) provided for fixing the reed switch on the cylinder. If it is a round deisgn cylinder addition sensor mounting kit will be required.
2) Operating Voltage (24 V DC or 230 V AC etc)
3) If any particular sensor wiring type is required (PNP or NPN)
4) Cable length and end connection option required (Open leads, M8 or M12 plug etc)

Reed switches are mounted on cylinders. When the magnet inside the cylinder barrel comes under the reed swith it causes the switch or make or break an electrcial circuit. This helps get positive signal and confirm that the cylinder are reached the required position.