What a 4 Inch Rockwool Block Does Better Than the Bigger Cubes
Four inches is the size most rooms run, and the reason is throughput rather than performance. The cube measures 4 x 4 x 4 in, arrives in sleeves of six, and stacks 72 to a case. Its hole takes the same starter plug as the rest of the line, so a rooted cutting drops in without cutting the wool open. Because the block is short, it wets through completely on a single shot and gives back a fast, even dryback. That makes irrigation decisions obvious rather than guessy in the first two weeks after transplant. The catch is that a flood table will keep the whole cube damp, since capillary movement covers a block this shallow end to end. On a table, run drip emitters into the top instead.
Moving a Grodan Pargro Block From Propagation Into Flower
A grodan pargro block is meant to be a stage, not a destination. Cuttings root in a plug for ten days or so, then sit in the block through veg while the root mass fills the corners. The whole block lands on a slab at flip. Nothing gets disturbed, because the roots grow out of the base rather than being pulled from it. The foil wrap handles the sides, so the only exposed wool is the top face where evaporation is useful. Sleeves of six are the reason this size ends up in small rooms as well as big ones. Pargro sits below the Grodan Delta wool on fibre spec, and in a room chasing tight crop steering that difference is real.
Key Features
- Four inch cube: The standard veg block size, short enough to wet through and dry back on one shot.
- Sleeves of six: Breaks a case down into handling units that fit a propagation bench.
- Pre-drilled hole: Accepts a rooted starter plug with no cutting and no root disturbance.
- Foil wrapped sides: Blocks light on four faces so evaporation happens only at the top.
- Inert stone wool: Contributes nothing to the feed, leaving pH and EC entirely under your control.
- Transplants onto slabs: The whole block moves at flip without breaking the root mass.
Technical Specifications
| Specification | Value |
|---|---|
| Brand | Grodan |
| Product Line | Pargro Quick Drain |
| Part Number | 328446 / 328446-S |
| Format | Block with hole |
| Dimensions | 4 x 4 x 4 in |
| Hole | Pre-drilled for a starter plug |
| Material | Basalt stone wool, inert |
| Wrap | Black and white foil, sides sealed |
| Case Count | 72 blocks |
| Sleeve Count | 6 blocks |
| Drainage | Balanced drain with moderate water holding capacity |
| Suitable Systems | Drip irrigation, hand watering, transplant onto slabs |
| Nutrient Contribution | None, the substrate is inert |
