Difference Su Carburetors Hd6 And Hs6 In Spanish, What Is The Difference Between The Possessive Adjectives Vuestro And Su?

In Spanish, what is the difference between the possessive adjectives vuestro and su? - difference su carburetors hd6 and hs6

Your (s)-su (Pl)
su (s)-you (plural), their
What is the difference if the two means that your (pl. )??????????