Dulux AutoSpeed High Build 1K Primer is a single pack primer that may be thinned prior to use. It is to be used as a primer for substrates such as mild steel, aluminium, steel and fibreglass. It may also be used over sound existing finishes. These surfaces should be cleaned and sanded prior to priming. Note: The aluminium surface requires suitable preparation. It is recommended that the adhesion over aluminium is checked before using this product.