This Malaysian Standard specifies the characteristics and performance requirements for masonry units manufactured from clay for use in masonry construction (e.g. facing and rendered masonry, load bearing or non-load bearing masonry structures, including internal linings and partitions, for building and civil engineering). This standard is intended to apply to two groups of fired-clay masonry units: a) LD units (see 3.4 and 5.2) comprising: i) clay masonry units with a gross dry density of less than or equal to 1 000 kg/m3 for use in protected masonry. b) HD units (see 3.5 and 5.3) comprising: i) all clay masonry units for use in unprotected masonry; ii) clay masonry units with a gross dry density of greater than 1 000 kg/m3 for use in protected masonry.