Component of the flagellar switch. Binds CheY-P and increases its hydrolysis rate in vitro. May function constitutively to remove CheY-P around the flagellar switch to maintain an optimal level of CheY-P whereas CheC may function after addition of an attractant to cope with increased levels of CheY-P. The switch is localized at the base of the flagellar motor, in or near the C-ring, attached to the MS-ring. Belongs to the FliN/MopA/SpaO family.