Gasjac recessed gas water heater weather box
The box is made from galvanised sheeting. Dimensions are 750x450x220 as standard, which means it will fit almost any gas water heater. The flue hole is 110 mm or 130 mm.
A model without the hole at the top is made in which we house our Rinnai gas water heaters as shown below.
This was a surface mounted application.