Vandoren BD4HD, BD5HD, BD6HD Bb Clarinet Mouthpieces

Wait, what the heck is HD? Are mouthpieces now measured the same way my television resolution is? No, in this case "HD" stands for "High Density." The material used is a different, more dense mix of rubber and...I don't know what. So I asked Vandoren what the material is. Everyone at Vandoren kind of smirked and shrugged. I'll just call it Vandoren Voodoo Rubber™ and move on. But one thing I gotta tell you — these mouthpieces are HEAVY. Here's a photo of the same mouthpiece (a BD5 in this picture) in both a non-HD and HD variety. As you can see, the HD mouthpiece is a little under 50% heavier than its on-a-diet sibling. So what? What difference does the HD material make? I tried a BD6 in both HD and Regular (SD?) varieties. I feel the sound I get from the HD has a presence, a core, a center, maybe even projection, that the SD version does not. If feels more responsive to the same reed. Basically it took my sound and made it "more" my sound. I'd like to hear your feedback if you try this back to back. Put it in a review, even if you didn't buy it from me, so we can all learn from each other. Deets: BD4: Tip Opening: 115.5 (Medium), Facing Length: Medium Long BD5: Tip Opening: 113 (Medium), Facing Length: Medium BD6: Tip Opening: 121.5 (Medium-open), Facing Length: Medium