Constrained Layer Technology formed the original 3D2, which consisted of two layers of aluminum with a viscoelastic "filling" - essentially an audiophile Oreo. Upon listening, it was evident that a stack of four or two yielded the best sound.

The gen1 3D2 was sold in boxes of 16. The second generation 3D2 consisted of 7 layers. It was better than two 3D2 OGs. Les discontinued selling gen1 3D2s when the newer gen2 3D2s in boxes of 8 became available. Recently, going through the warehouse, a bin of NOS (new old stock) boxes were found (new old stock - like many tubes). They are ten years old.