Zelta Adjustable Door Window Lock Stopper Wedge with Rubber Covered for Sliding Window (Bronze, Pack of 2) Iron + rubber; Window stopper are covered with rubber, effectively increase the friction for the better use and would not damage or scratch your window and avoid any annoying noise Designed for horizontal sliding windows, Not for vinyl windows; Total length: 2.36"; Width: 1.57"; Height: 0.59" By adjusting window stopper knob; Fit on window track spacing from 1.02" to 1.69"; Track high more than 0.59", in case affecting the stability of the security lock No tools are needed; Improve air circulation; Keep your child safety; Both use in keeping the window closing and partial opening Close or open the window before installing window stopper; Insert the leg closely to the window groove ; Turn the knob clockwise until the product is secured Use 2 lock in heavy window/door for adding security; This product does not guarantee total crime prevention; Please use this product along with other crime prevention tools