They adjust from about 29.5 inches up to 46 inches, covering narrow doorways through openings that measure 46".
Common heights are approximately 30 inches and 36 inches.
They come as pressure-mounted models for tool-free, temporary installs and as hardware-mounted (screw-in) options for more permanent or stair installations.
Many models offer tool-free, pressure-mounted installation; others provide hardware kits and require tools for a screw-fixed, more stable installation.
Typical features include an auto-close hinge and a dual/double-lock mechanism that requires an adult action to open—often designed for one-handed operation while remaining child-resistant.
Some models have visible red/green indicators on both sides to show proper tension and guide pressure-mount adjustments.