Cretex LSS Internal Manhole Chimney Seal is a mechanical seal installed on the frame and grade ring sections of sanitary sewer manholes.
These seals eliminate and prevent manhole frame-chimney inflow. During wet weather, clear water enters manholes through deteriorated and broken frame-chimney joints, which may burden the collections system.
Each seal is made up of a high-grade rubber sleeve and stainless steel expansion bands, which can be easily removed and reinstalled to allow for future manhole adjustments.
It has a 50-year design life and is available in four widths, allowing complete chimney coverage of up to 24 vertical inches with a single seal.
To read more : http://www.mswmag.com/editorial/2016/09/cretex_lss_internal_manhole_chimney_seal