Ideally, sealed goggles are the best choices, as there is no gap to allow BBs in. Most fields (particularly if they're paintball fields) will only accept paintball goggles for insurance purposes. Non-paintball field games will allow ballistic goggles. Some will only allow goggles, others will allow shooting glasses with ballistic lenses.
But in the end, it comes down to protecting your eyes. $50-ish for a pair of good ballistic goggles is worth it.
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