  We conjecture dualities among branes that consist of Neveu-Schwarz sector
fields, such as NS5-branes. Two branes are dual after compactifications on
spheres with gauge fluxes. The conjecture follows from simple considerations on
string worldsheet theories. For some NS5-branes, we get level-rank dualities of
Chern-Simons theories. Application of the dualities to a newly found brane in
heterotic string theory reveals surprising properties of the worldvolume theory
on it, for which we give evidence from anomaly inflow.
