Hi Hans, what is the purpose of the moffset key for \setupmathstackers? There is a definition where you assign a dimension to the key \definemathstackers [\v!wide] [\c!moffset=\thickmuskip,\c!mathclass=\s!rel] but this makes no sense as can be seen in the code below because it isn’t used. \unexpanded\def\math_stackers_unstacked_normal#category#codepoint% {\begingroup \edef\currentmathstackers{#category}% \edef\p_moffset{\mathstackersparameter\c!moffset}% \ifx\p_moffset\empty \else \mskip\scratchmuskip \fi \ifmmode\math_class_by_parameter\mathstackersparameter\else\dontleavehmode\fi {\usemathstackerscolorparameter\c!color \Umathchar\zerocount\defaultmathfamily#codepoint}% \ifx\p_moffset\empty \else \mskip\scratchmuskip \fi \endgroup} Wolfgang