  We present general formulas for the oblique-correction parameters $S$, $T$,
$U$, $V$, $W$, and $X$ in an extension of the Standard Model having arbitrary
numbers of singlet, doublet, and triplet quarks with electric charges $-4/3$,
$-1/3$, $2/3$, and $5/3$ that mix with the standard quarks of the same charge.
