Grodan Expert Slab 20/75 36 x 8 x 3 in | Single Slab, Stone Wool

One Expert Slab 20/75 Rather Than a Case

The slab is 36 in long with a 20 by 7.5 cm section, which reads as 8 by 3 in. Metric and imperial describe the same piece of wool, and the designation is the cross-section stated in centimeters. It ships in the printed foil it is meant to be planted in. Grodan item 320565 covers this format, and the SKU for one slab is 320565-S. Wool is inert stone wool with the advanced wetting agent that holds content and EC even along the length. There is no nutrient charge to flush out before the first feed. Resaturation after a dryback is quick enough to run a tight wet-dry swing. A single slab takes three plants at standard spacing, or two where the canopy wants the room. Soak it to full saturation for at least half an hour before anything is planted. The seams go taut when it is genuinely full.

Where Vertical Fiber Matters on a Mid-Run Swap

Replacing one position mid-cycle only works if the new wool behaves like its neighbors. Fiber direction is the reason it does. Water that travels down instead of along lets the new slab reach content on the same irrigation schedule as the ones either side. Without that it would lag and pull the whole line out of step. Cut the drain slit in the same place as the rest of the row, at the low point under the seam. Match the plant hole to the block going into it and keep the blade off the wool when you open the foil. Drip stakes go one or two to a hole and must stop short of the base. Then watch that position against a neighbor for a few days. A fresh slab and a six-week-old slab do not dry back identically at first. Expect to irrigate it slightly less until the root plate catches up. The limit is the unit economics, since one slab at a time costs more per slab than a bundle. Treat it as a repair and trial unit rather than how a room gets stocked.

Key Features

• Single slab: One unit for a trial position or a mid-cycle replacement in an established row.
• 20/75 section: The designation is the metric cross-section: 20 cm wide by 7.5 cm deep.
• 36 in length: Matches the bench spacing already set up for the rest of the row.
• Vertical fiber wool: Reaches content on the same schedule as the slabs either side of it.
• Inert, flush-free: No nutrient charge in the wool, so the first feed is the feed you mixed.
• Printed foil wrap: Light-excluding and labeled, planted as it comes out of the box.

Technical Specifications