There are different 'types' of Pex tubing (A, B, C). Pex A (wirsbo) will expand as stated earlier. I'm in Oregon and we use Wirsbo for most residential applications and I've installed up to 2" Wirsbo in really cold weather, it's harder to work with and it takes longer to shrink back on the fittings. Using a torch lightly on the rings will shrink them quickly so you can turn the water on sooner. I've yet to see or hear of Wirsbo freeze breaking but I'm sure it can happen under extreme conditions. The fittings and collars(rings) are the weakest link in the Wirsbo System. Rehau is a great product as well, expensive though.