SledgeHammer's Mechanical Stage tool allows cementing of casing string in two stages. These tool set the standard for reliability, cost effectiveness, and ease of use with outstanding built-in features and quality. They are the tools of choice when drilling requirements call for proven technology and low risk. The compact, simple design minimizes the number of moving parts and makes the tools easier to handle.

The tool's clear opening and closing indications at the surface accommodate the hydraulic conditions of the well for safer, more efficient operations. The internal sleeves increase reliability and prevent premature opening from formation restrictions on applied pressures. It reduces total pumping pressure in long casing strings.

These are available in 4 1/2" to 13 3/8"

Source :- https://www.sledgehammerasia.com/stage-cementing-tools/stage-cementing-tool.html