The bowls used must rigorously follow the protocol set out by the F.I.B, which is included in the Regulations relating to the approval and conformity check of the bowls.
They must be exclusively made of metal or metal alloy,but their chemical composition has to be homogeneous (a very small variation is tolerated for the plug).
They can be completely hollow or filled. In the latter case the bowls must be filled with a substance or homogeneous mixture of inert substances. They must not contain any liquids, nor any compositions which could become unstable (gas) and could be dangerous.
The filling of the bowls must be statically balanced and that balance must be maintained after the bowls have been used.
They must :
• be spherical, with a tolerance of of +/ 0.1 mm;
• be balanced, with a tolerance not above 1.1% of the weight of the bowl ;
• have the hardness within the values of 20 and 30 on the Rockwell scale with the weight of 150 kg, with a lower tolerance for the plugs (minimum 17 on the Rockwell scale);
• have a diameter between 90 mm. and 110 mm;
• have a weight between 900 gr. and 1200 gr.
To be coloured, a bowl can be composed of another material on its surface.
The proportion of this other material mustn’t exceed 27% of the bowl’s surface.
It mustn’t alter its hardness. These inlays mustn’t either come off or plunge into the bowl.
This material must be part of the filling of the bowl.5
Excluded from the above rules on hardness of bowls are the target bowls and obstacle bowls used in throw competitions and in training schools.
Children (14 and Under) and women players can use smaller and lighter bowls. Each National Federation will select what it considers to be the most suitable for its own territory.
For International Competitions in these categories :
• Minimum diameter : 88 mm.
• Minimum weight : 800 gr