concavity portion the concavity portion has an outer surface 32 and an inner surface 34 the inner surface contains a concavity 40 with a concavity end 42 that is also one attachment point for the upper body 100 the concavity may contain structural ribs to enhance the geometric stability of the glide and the concavity also functions to allow elastic deformation of the glide due to impact forces providing impact absorption in severe service this provides means for absorbing impact forces normal to the tubular product axis on a surface offset from and surrounding the tubular product as shown in fig9 10 and 11 the concavity inner surface is also integral with the attachment extension portion that has an attachment extension 44 with a first end 46 where it is molded with the concavity portion inner surface to form the main body and a second end 48 that is the second attachment point for the upper body 100 between the main body outer and inner surface there is a countersink opening 50 located centrally in the attachment extension first end 44 the countersink opening is sized to allow through passage of the bolt threaded portion 64 while keeping the bolt head portion 62 within the countersink the opening may not include a countersink in which case the bolt head portion 62 may protrude from the main body outer surface the engagement means is shown in cross sectional view of a first embodiment in.