In the process of perfecting the umbrella, an oval design was considered. However, as this shape could make it difficult for users to fend off side attacks, the round design was eventually selected. The finished flexible umbrella is easy to use even in narrow spaces like train aisles. "We haven't heard of other rail operators introducing similar weapons," said a JR West representative. Previously, JR West equipped different trains with different weapons, such as riot shields, anti-blade gloves and knife-proof vests. But these traditional tools did not go down well with crew members. A typical complaint was that the "acrylic shield is so heavy" or that the protective gear "does not give the user a sense of security as it is impossible to keep a safe distance from a person with a knife."