Check the listing for details. DCC Concepts ~ Slim Vertical Mounted Magnetic Detection Sensors ~ 4 Pcs ~DCP-TMS. Condition: New. Listed at 15.23 USD. Iron Planet Hobbies DCCconcepts ~ Slim Vertical Mounted Magnetic Sensors ~ 4 Pieces ~ DCP-TMS (normally off or N.O. momentary type) These detectors have been designed to be very easy to install. Only 4mm in diameter, they will fit between the ties of Peco Code 100 and Code 75 track. They are “Normally Off” and are triggered by a small magnet that is attached to the loco or rolling stock. While it is always good to use smaller magnets and get the magnet as close as possible to any sensor such as this, we find that even with quite a small magnet we can get reliable results from up to 10mm away. Ideal for all detection and to trigger devices such as Cobalt Point Motors or Alpha. Physical Characteristics Length of sensor: 15mm Width of sensor: 4mm Length of wire: 300mm Quantity in pack: 4 We are an authorized DCCconcepts dealer.Thanks For Looking!