5.2.1. The maximum distance between the poles of YOKE shall be 200 mm. In each area inspected, the contact points will be crossed two by two so that the part is successively magnetised in directions perpendicular to each other. 5.2.2. Instruments in direct current will be used preferably. 5.2.3. The surface shall be examined 100%, within the geometric limits of the part. 5.2.4. YOKE application is not allowed in complex geometry zones where the contact between poles and surface is partial (i.e. fillet and similar). 5.2.5. The magnetic particle material shall be distributed uniformly over the area of examination during magnetisation, to be maintained for at least 4 sec.