Like the fifteen years older brother tank, the container walls of the HAASE T400 consist of glass fiber reinforced plastic, so-called GRP. A material which is extremely strong when shaped, it will never rust and is of long-lasting durability.

As a composite material, the GRP has self-insulating capacity, whereby the insulation of the entire tank surface ensures optimal heat storage over several days. The insulation is protected by a solid GRP covering.