Electric central heating boiler

I would like to buy an Electric Boiler for Central Heating with the following specifications:
1. Tank Sheet Thickness: 5 mm or 4 mm
2. Insulation Thickness: 30 mm
3. Tank Material: Pure Stainless Steel
4. Tank Volume: 250 Liter of water
5. Outer Jacket: Stainless Steel
6. With 3 Screw Plug Coils I will recommend your Company to all of my friends.