Everbuild acoustic sealant amp adhesive ac50 everbuild ac50900 ac50 acoustic sealant amp adhesive is a high strength permanently flexible sealant and adhesive specifically formulated for sealing and bonding plasterboard and other kraft lined insulation boards typically used for walls ceilings and dry lining applications independently tested to bs en iso 1403 everbuild ac50900 acoustic sealant amp adhesive 900ml ac50