Hi, there is no loop cap on the old version, but it would still fit. This should make it more leak proof. However, I have to say that the 3.0 version makes an annoying sound when the air goes into the bottle. I use it a lot in the office, so it's really annoying. The old one didn't have this problem. Otherwise, I think the bottles are great and if you store them upright in your backpack, they don't leak, but they do drip when lying down or on your head. The 3.0 leaks less but makes more noise when drinking. Hope this helps...

Servus, if you mean a screw cap to cover then no, the visible thread groove in the picture is the internal thread for the drinking adapter.