[ɚ]

Height: mid
Advancement: central
lip rounding: rounded
Tense/lax: lax

NOTE: only in unstressed syllables.

pertain
surround
runner
ergonomic
luxury
treasure
under
ferocious
cursor
flirtatious
countered
Saturday
percussion
mattered
Herbert
harbor

Allographs

labor
lunar
urbane
winner
flirtatious
martyr