The Maine Coon is widely recognised as one of the largest domestic cat breeds, and the GCCF describes it as the largest domestic breed it recognises. That does not mean every Maine Coon is larger than every cat of another breed. Individual body length, frame and weight vary, and different record categories measure different things. The longest cat is not necessarily the heaviest or tallest. When choosing a pet, avoid making exceptional size the main goal: suitability for your home, temperament and responsible breeding are more useful criteria.
Large cats need equipment that supports their actual build. Check both load limits and room to turn, stretch or lie comfortably. A generously proportioned bed or tray can be a more useful investment than an imposing tower whose platforms are too small for the cat using it. When comparing size claims, ask whether the figure describes body length, tail-inclusive length or weight; those measurements cannot be ranked interchangeably.
For product comparisons alongside this advice, see Velvet Nest and Sterling Court litter tray. The details below explain their sizes and uses.
Further reading: gccfcats.org; pdsa.org.uk.
Velvet Nest
Sterling Court litter tray
Taj-MeowHall