  The richness of 5d $\mathcal{N}=1$ theories with a UV fixed point at infinite
coupling is due to the existence of local disorder operators known as instanton
operators. By considering the Higgs branch of $SU(2)$ gauge theories with $N_f
\leq 7$ flavours at finite and infinite coupling, we write down the explicit
chiral ring relations between instanton operators, the glueball superfield and
mesons. Exciting phenomena appear at infinite coupling: the glueball superfield
is no longer nilpotent and the classical chiral ring relations are quantum
corrected by instanton operators bilinears. We also find expressions for the
dressing of instanton operators of arbitrary charge. The same analysis is
performed for $USp(2k)$ with an antisymmetric hypermultiplet and pure $SU(N)$
gauge theories.
