Stage Plus 4 consolidates the phonemes and graphemes taught in Stages 1 - 4. 

It explicitly teaches two letters, one sound - ll, ss, ff.  Simple one syllable words with a short vowel phonemes. 

Adding 's' to CVC words introduces morphology, for example, dog + s (dogs), run + s (runs). 
 
Another great Bingo game to practise single word reading.