Price history on Walmart.com for
Uxcell 10 Sets Screw Surface Mount Wired NC Magnetic Door Contact Reed Switch Alarm
See on WalmartProduct info
Contact Type : NC,Normally Close Contact Capacity : 0.5A(Maximum Switch Current) Voltage : DC 100V Rated Power : 10W Action Distance : 10(+/-5)mm Each Size(Approx) : 2.5" x 0.51" x 0.51"(L*W*H) Mounting Hole Dia. : 4mm/ 0.16" Wire Length(Each) : 27cm/ 10.6" Color : White Housing Material : ABS Weight : 199g Package Content : 10 Sets x Magnetic Switch; 40 x Installation Screws
... read more.