In the game manual definitions, the "Vision Target" is defined as:
a retro-reflective target, made of 3M 8830 Silver Marking Film, that may be used by ROBOTS to sense FIELD elements.
The 3M website says that you should be able to purchase it at certain retailers.
Here is the link.
AndyMark has a similar reflective tape which was used in the 2012 game, however seeing as the brand has changed, I don't think that you should rely on that being the same as the brand listed in this year's manual.
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