Grodan Bro-Block Improved GR6.5 4" x 4" x 2.5" Unwrapped (216/Case)

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GrodanSKU: B50205

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Grodan Gro-Block Improved GR6.5 4" x 4" x 2.5" Unwrapped (216/Case)

The Grodan Gro-Block Improved GR6.5 4" x 4" x 2.5" Unwrapped (216/Case) is a compact professional stone wool growing block designed for hydroponic cultivation, young plant development, and precise root-zone management.

Each GR6.5 measures 4 × 4 × 2.5 in (10 × 10 × 6.5 cm) and provides approximately 0.65 L of stone wool substrate. The blocks are supplied unwrapped and include a planting hole for compatible rooted plugs. Each case contains 216 blocks.

Key Benefits

  • Professional Grodan Improved stone wool block.
  • Dimensions: 4 × 4 × 2.5 in (10 × 10 × 6.5 cm).
  • Approximately 0.65 L of substrate per block.
  • 216 blocks per case.
  • Supplied unwrapped.
  • Integrated planting hole.
  • Uniform water and EC distribution.
  • Compact, responsive root zone.
  • Compatible with drip irrigation and precision fertigation.
  • Suitable for high-density hydroponic cultivation.

Why Choose the GR6.5?

The GR6.5 offers the same 4 × 4 in (10 × 10 cm) footprint as larger 4-inch Gro-Blocks but with a lower 2.5 in (6.5 cm) profile.

Its compact substrate volume responds quickly to irrigation and dry-back adjustments, making it useful for growers who want precise control of root-zone moisture and EC.

Grodan Improved Technology

Grodan Improved combines an optimized fibre structure with an Advanced Wetting Agent to improve initial saturation and promote more uniform water content and EC throughout the block.

This helps growers manage irrigation, nutrient delivery, and dry-back more consistently during the crop cycle.

What Does “Unwrapped” Mean?

The GR6.5 is supplied without an outer plastic or foil covering, leaving the stone wool exposed.

This format is useful in trays, gutters, benches, and other systems where the growing environment is managed separately.

Ideal Applications

  • Hydroponic cultivation
  • Rooted propagation plugs
  • Young plant production
  • Drip irrigation
  • Precision fertigation
  • Indoor horticulture
  • Commercial greenhouses
  • Controlled-environment agriculture
  • High-density cultivation

Product Specifications

Specification Details
Brand Grodan
Product Gro-Block Improved GR6.5 Small 4"
Type Stone wool growing block
Dimensions 4 × 4 × 2.5 in (10 × 10 × 6.5 cm)
Substrate Volume Approx. 0.65 L
Planting Hole Yes
Outer Wrapping Unwrapped
Growing Media Stone wool
Quantity per Case 216 blocks
Primary Use Hydroponic cultivation and root-zone management

How Do You Use the Grodan GR6.5?

Hydrate and condition the block according to your nutrient and irrigation program before transplanting.

Place a compatible rooted plug into the planting hole, then adjust irrigation according to plant demand, environmental conditions, EC, water content, and desired dry-back.

GR6.5 vs. GR10

The GR6.5 measures 4 × 4 × 2.5 in (10 × 10 × 6.5 cm) and offers approximately 0.65 L of substrate.

The larger GR10 measures 4 × 4 × 4 in (10 × 10 × 10 cm) and offers approximately 1 L.

The GR6.5 provides a smaller, more responsive root zone, while the GR10 offers greater rooting volume and moisture capacity.

Frequently Asked Questions

How many GR6.5 blocks are included per case?
Each case contains 216 blocks.

What are the dimensions?
Each block measures 4 × 4 × 2.5 in (10 × 10 × 6.5 cm).

What is the approximate substrate volume?
Each block provides approximately 0.65 L of stone wool.

Does the GR6.5 have a planting hole?
Yes. This version includes a planting hole for compatible rooted plugs.

What does Unwrapped mean?
The stone wool block is supplied without an outer plastic or foil covering.

Can it be used with drip irrigation?
Yes. The GR6.5 is well suited to drip irrigation and precision fertigation.

Order Confirmation

As soon as your order is placed, an order confirmation will be sent to the email address you used to place the order. This means we have received your order and payment. Payment is captured as soon as the order is placed. In rare cases, if the product is on backorder or unavailable, we will contact you and ask if you would like to wait for the product to become available, switch your product, or have your payment refunded. If the item is available for shipment we will submit the order for processing and arrange shipment. Please see current estimated lead times on the product page for each product.

Shipping

Most products ship within 1 to 3 business days. Some items might take longer as they are delivered from our warehouse in Vancouver. As soon as we receive your tracking number, we will send it over to you.

Free Shipping

Free shipping is available across all provinces throughout Canada for orders over 149$.

International Orders

Nearly all of our brands can be shipped internationally using FedEx, UPS, USPS, DHL or other couriers. Most quotes can be obtained at checkout. If not, you can email us at info@canadagrowsupplies.com for some more information on shipment. Items shipped internationally from the USA may have VAT, duties, taxes, and/or local charges due at delivery. These charges are the responsibility of the customer and not Canada Grow Supplies Inc.

Cancellations

If you need to cancel your order, we recommend reaching out to us ASAP. We charge a 2.9% (credit card), 3.5% (PayPal), 4.0% (PayPal International), 4.1% (American Express), or 6.5% (Shop Pay Installments or Sezzle) order cancellation fee after the order was received. We can accommodate most requests, but due to the different time zones and schedules that our warehouses ship from, sometimes the cancellation request may not reach the warehouse in time before the product ships. Once the item has been arranged to ship or has shipped, the package will be treated like a 'return' and is subject to ship-back fees and restocking fees. If you purchased 'Route Package Protection', this can not be refunded after the order has shipped.

Returns

In order to make sure you are completely satisfied, we can send you a return label within 14 days of receiving the order. This is to guarantee that you are happy with the product. Some products might require a 10-25% restocking fee. Please visit our full return policy.

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2. We’re a small, Canadian, family-owned business.

Our small team overlooks every customer and their orders to ensure they are satisfied with their products. We answer the phone and website chat, and if we don’t, we get back to you within 6 hours or less! We even throw in some freebies at random.

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5. Reliable International Shipping

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Adding Route Package Protection to your order at checkout means that your order is protected against being lost, damaged, or stolen. In the unfortunate instance that you experience one of these inconveniences, you can report an issue with Route and they will work with you to make sure you get the resolution you prefer.

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