embodiments shown and described as modifications and equivalents will be apparent to one skilled in the art in the drawings and specification there have been disclosed illustrative embodiments and although specific terms are employed they are used in a generic and descriptive sense only and not for the purpose of limitation fig1 is a side sectional view of an example of a wellhead assembly 10 being formed by inserting a high pressure housing 12 into a low pressure housing 14 a weld 16 on the high pressure housing 12 of fig1 attaches an upper portion 18 to a lower portion 20 where the lower portion 20 extends downward and into a wellbore 21 similarly the low pressure housing 14 includes a weld 22 attaching an upper portion 24 to lower portion 26 in the example of fig1 the lower portion 26 is anchored within a sea floor 27 a transition 28 on the upper portion 18 indicates where its thickness changes below the transition 28 the thickness of the upper portion 18 is substantially the same as a thickness of the lower portion 20 whereas above the transition its thickness increases to a maximum width to define a middle section of the high pressure housing 12 an upper terminal end of the.