Product for heat containment per rack unit?

[David Hubbard <dhubbard () dino hostasaurus com>]

Curious if anyone has knowledge of a vendor / product designed to make it possible to use back-to-front cooled 
equipment in racks that need to be ‘sealed’ for heat containment reasons?  I’d envision this looking like some kind of 
adjustable depth sleeve, to get the cold air to the equipment, and perhaps a brush strip opening to allow power cables 
in?

Thanks!