The glyph is not a composition. Its width in East Asian texts is determined by its context. It can be displayed wide or narrow. In bidirectional text it is written from left to right. When changing direction it is not mirrored. The word that U+044A forms with similar adjacent characters prevents a line break inside it. The glyph can be confused with one other glyph.
The Wikipedia has the following information about this codepoint:
The letter Ъ ъ (italics Ъ, ъ) of the Cyrillic script is known as er goläm (ер голям – "big er") in the Bulgarian alphabet, as the hard sign (Russian: твёрдый знак, romanized: tvördý znak, pronounced[ˈtvʲɵrdɨjˈznak], Rusyn: твердый знак, romanized: tverdyj znak) in the modern Russian and Rusyn alphabets (although in Rusyn, ъ could also be known as ір), as the debelo jer (дебело їер, "fat er") in pre-reform Serbian orthography, and as ayirish belgisi in the Uzbek Cyrillic alphabet. The letter is called back yer or back jer and yor or jor in the pre-reform Russian orthography, in Old East Slavic, and in Old Church Slavonic.
Originally the yer denoted an ultra-short or reduced mid rounded vowel. It is one of two reduced vowels that are collectively known as the yers in Slavic philology.