This wraps the ObjectARX AcDbAssocFilletSurfaceActionBody class.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.AssocActionBody
        Autodesk.AutoCAD.DatabaseServices.AssocParamBasedActionBody
            Autodesk.AutoCAD.DatabaseServices.AssocSurfaceActionBody
                Autodesk.AutoCAD.DatabaseServices.AssocFilletSurfaceActionBody

Public Class AssocFilletSurfaceActionBody
Inherits AssocSurfaceActionBody

public class AssocFilletSurfaceActionBody : AssocSurfaceActionBody;