4-Button Switch for Switch Flex Controller (with instructional video)

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This is a four-button switch for use with the Flex Controller, an input assistance device developed for the Nintendo Switch.
It's a modified commercial PlayStation controller.
Compared to previous listings, the wires have been lengthened. You can use it at a distance from the Flex Controller.

Please connect it to the Flex Controller for use. You can see how it works here:
https://youtube.com/shorts/9BANCFqUg9o?si=YjHw4nh5z-HqRlHQ

The buttons are large and have a short stroke.
It was created to allow individuals with C4 spinal cord injuries to differentiate button presses. I play "The Legend of Zelda: Tears of the Kingdom" using the same setup.
You can differentiate the buttons without looking at them.
Please see the dimensions below and the photos.
I think even children could use it with their feet. Maybe you could play Taiko no Tatsujin with four buttons.

I will provide support on how to use it via email.
If you are in Osaka, southern Kyoto, eastern Hyogo, or northern Nara, I can provide a demonstration with the Flex Controller and switch for a fee and actual transportation costs. If you'd like to try it out, or are wondering if your child can use it, please feel free to contact me! Professionals in the field of welfare (such as occupational therapists) are also welcome to contact me.

Distance between the centers of the buttons: Approximately 9cm
Button size: Approximately 6cm in diameter
Button stroke (press depth): Approximately 0.2cm
Overall size: Approximately 20cm x 20cm x less than 3cm
Length of the φ3.5mm mini-plug wire: Approximately 1.3 to 1.4m
The commercial controller used for modification is a used item.
There may be scratches and dirt.
Please refrain from purchasing if you are looking for a new or pristine item.