Everbuild Black Jack® 903 Bitumen Trowel Mastic is a black, heavily filled, bituminous compound with added fibres for reinforcement, that is applied by trowel. It is used primarily for patching holes in roofs and bituminous coatings. The product forms a surface skin, but the mass below remains soft to allow for moderate movement.Select Option 1 Litre2.5 Litre5 Litre Add to Basket Quantity