Will these fit IKEA, Bekant, or non-standard filing drawers?

Not always. Multiple subreddit threads we read flag that some IKEA filing drawers and shallower desk drawers won't accept standard 11 3/4" letter hanging folders without a frame insert, and that some 'letter-sized' drawers are actually a hair too short. If you're filing into anything other than a dedicated letter or legal filing cabinet, measure the rail-to-rail width before ordering.