Hello Chad:
DMX 1-Step Underlayment (original) had 8mm dimples. This underlayment has been discontinued and replaced with DMX 1-Step 2.0 with 4mm dimples.
The new DMX 1-Step 2.0 provides a higher dimple density and a lower dimpled profile, increasing the compressive strength to 12,000 lbs per square foot. These modifications ensure that the product is more rigid and therefore suitable for (click) vinyl plank flooring (≥5mm), as well as laminate and engineered hardwood.
DMX 1-Step Underlayment (original) has been discontinued approx. 2 years ago, and DMX 1-Step 2.0 has been its replacement ever since then.
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DMX