CGC Synko® Concrete Fill Coverage: 12 L of material per 15 kg bag Application: Fill, level, and patch voids in interior concrete ceilings and walls. CGC Synko® Concrete Fill is an easy to mix, quick-setting, lightweight fiberglass reinforced plaster compound that can fill voids up to 1" thick without shrinkage or cracking. It can also be used to pre-fill or patch plaster or drywall surfaces. Data Sheet