The interlocking caps which suffer, especially in the ''conical'' version, from problems of wear on the surfaces with loss of tightness, have been followed, with a trend established since the beginning of the '900, by the caps with screw closure (''threaded cap''), which are still among the most common today. A return of the interlocking caps took place in the '40s with the introduction of metal caps closed with friction on special rings (trend introduced by the [[Parker 51]]). | The interlocking caps which suffer, especially in the ''conical'' version, from problems of wear on the surfaces with loss of tightness, have been followed, with a trend established since the beginning of the '900, by the caps with screw closure (''threaded cap''), which are still among the most common today. A return of the interlocking caps took place in the '40s with the introduction of metal caps closed with friction on special rings (trend introduced by the [[Parker 51]]). |