Get width ofNode

Hi All

how would you get the width of an object that has being scaled with ofnode?

i am trying thing like this but no luck so far

ofMatrix4x4 test;
test.setRotate(testNodes[0].getOrientationQuat());
test.setTranslation(testNodes[0].getPosition());
test.scale(testNodes[0].getScale());
ofVec3f pointab(xb,yb,zb);
ofVec3f transformed_pointv = pointab * test;

Best
Ben