I like buying glass from Arrow Springs because they have the best pricing for clear rod and tubing. But they seem to be chronically out of supply in any size I want (7mm, 8mm, 19mm). Expected time for getting more 19mm in stock: 2-3 weeks from now. Here's what I don't understand: why the long lead time? Where's it coming from? Is the factory not producing it? Producing something else in its stead? Diverting their production to someone else who's paying more? I'm sort of curious about how this all works.