I needed new jeans. I went to the same store as always, chose the same size and model... and they didn't fit. I tried a different pair, the same. Then I compared them to the ones I was wearing. The jeans at the bottom (with the belt) are the ones I'm using now. The ones on top are new - same size and model, but quite smaller. Why don't they keep sizing consistent? It's a total headache. And I was at the store, so I was able to try on different sizes and models, but if you happen to buy on internet... it's just a gamble.
