Can these screw in dirt only

These are not meant for dirt. these are meant to be set in wet concrete and let dry for a permanent post mount

It'll fit just fine as long as you don't mind it overhanging an inch on each side...

Would the 4x4 one hold up fine with just one 4x4 attached exposed to wind? The only other thing attached would be roughly a 10"x10" piece of wood.

I only have 3' tall beams and used all 6", it really isn't that much more and to me, for the difference, I would use the larger Post.

what is the diameter of the spike at the bottom? I'm trying to "fix" broken original mounts...

Sorry, I didn’t measure the diameter of the spikes. My guess is 3/8 to 1/2 inch

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MTB 4"x3.5" 4PCS U Shape Fence Post Holder Black Powder Coated,Ground Spike Post Anchor Metal Concrete Post Anchor Deck Post Base

MTB 4"x3.5" 4PCS U Shape Fence Post Holder Black Powder Coated,Ground Spike Post Anchor Metal Concrete Post Anchor Deck Post Base

Product ID: 109956376

📏fits 3.5x3.5 inch posts perfectly

🖤black powder-coated rust resistance

🛠️12.5-gauge steel strength

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¥10752

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Sold byAmazon JapanDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

🖤 Secure your space with style and strength!

BUILT TO LAST - Crafted from heavy-duty 12.5-gauge steel for unmatched durability and stability.
PRECISION FIT - Designed specifically for 3.5 x 3.5 inch wooden posts with 10 pre-drilled holes for secure installation.
RUST PROOF ELEGANCE - Sleek black powder coating prevents cracking, peeling, and rusting—keeping your posts pristine.
VERSATILE RELIABLE - Ideal for porch railings, mailboxes, and deck posts—backed by a 100% satisfaction guarantee.
WOOD SAVING INNOVATION - U-shaped design separates wood from damp concrete, extending the life of your fence posts.

The MTB 4"x3.5" U Shape Fence Post Holder is a premium set of 4 black powder-coated steel anchors designed to securely hold 3.5 x 3.5 inch wooden posts. Engineered with 12.5-gauge steel and a rust-resistant finish, these post bases prevent wood damage by separating posts from concrete, ensuring long-lasting stability for decks, fences, and mailboxes.

Specifications

ASIN	B077QD9K97
Best Sellers Rank	#44,988 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #328 in Hardware Brackets
Customer Reviews	4.5 4.5 out of 5 stars (1,027)
Is Discontinued By Manufacturer	No
Item Weight	6.16 pounds
Item model number	GSPB3644
Manufacturer	MTB Supply Inc
Product Dimensions	4 x 4 x 1 inches

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