The New American Standard translates G0030, ἀγγείοις (angeíois) as 'flask', so I assume that is the translation you used. The KJV, for example, translates as the less descriptive 'vessel', and I have also seen 'receptacle' or 'container' in this verse. For fun, Wiktionary also includes the definitions jar, vase, pail, bucket, box, reservoir, coffin, sarcophagus, and body cavity. I am going to go out on a limb here and say that 'body cavity' is probably not what was meant.
For me, though, the most useful information is that this same word was used in Matthew 13:48 as well. Here, the NAS and KJV translators decided on the same English word, 'vessels'. Of the research that I have heard, I do not see anyone disputing that chapters 13 and 25 had different authors or wildly different time periods, so perhaps we can assume that the word had the same or similar meaning when it was used in each case?
In Matthew 13:48, Jesus is telling another parable, just like chapter 25. This time, the 'vessels' are large enough for at least one fish, and logically would be large enough to hold multiple fish. I can not say (someone can, just not me) what size fish the listeners were accustomed to seeing at that time, but the previous verse mentions 'every kind', so, again logically, the 'vessel' would have to be large enough to hold at least one of of the largest fish that the listeners would assume would be caught in the sea by net. I personally don't think we are talking Jonah large, but I really don't think we aren't talking just sardines either. So, how big was the vessel for the fish? The translation 'pail' seems to fit here, doesn't it?
And, if the same word, said by the same person, recorded by the same person, in the same culture, in the same time period, to similar sized groups, to people with similar mindsets, to teach a similar topic, is used, can we assume they have similar meanings? Let the reader decide.
Either way, I feel safe in assuming that the 'flask' of Matthew 25:4 would NOT fit on my key ring.