Abstract: An insulation device for surrounding the uninsulated, adjoining end portions of a preinsulated pipe comprising a plurality of axially extending cylinder segments adapted to be circumferentially joined to form a cylindrical insulating jacket around the uninsulated end portions. The cylinder segments in their undeformed states have a length slightly greater than the combined length of the uninsulated adjoining end portions. The cylindrical insulating jacket has an inside diameter generally conforming to the outside diameter of the uninsulated end portions and an outside diameter generally conforming to the outside diameter of the preinsulated pipe. Each cylinder segment has at least a first pair of rigid arcuate sections and a first resilient arcuate section sandwiched therebetween. The first resilient arcuate sections of all of the cylinder segments are longitudinally positioned in the cylindrical jacket to fall substantially in the same transverse plane.