CRC 121 Concrete Filler is a two part silica based epoxy. Once mixed, the putty can be easily moulded to form permanent watertight repairs with a smooth finish to concrete, brick, mortar and plaster. It adheres well to wet surfaces and is suitable for most underwater repairs. In cured form CRC 121 Concrete Filler is many times harder and more impact resistant than concrete, has a similar consistency and colour to new concrete, and has excellent chemical and UV resistance.