For me it is OOTW as taught to me by my late magical mentor back in the early 80's.
I also do a little effect where i take five black spot cards and the same five red spot cards, place one set of cards face down whilst the spec then places their set face up on top of mine. The low and behold the spec has correctly matched their cards with mine. Again this was taught to me by my mentor over 25 years ago.
Very simple to do and very effective. But then most tricks are.
