Slater Atlas Stone Lightening Insert

Name: Slater Atlas Stone Lightening Insert
Brand: Slater Strength
Rating: 5.0 (3 reviews)

The Slater Atlas Stone Lightening Insert is a high-density foam core that gets mixed into the concrete pour for a Slater Atlas Stone mold, hollowing out an air cavity to cut the finished stone’s weight without shrinking its overall size. It’s sold in four sizes – 6”, 8”, 10”, and 12” – reducing weight by roughly 10, 25, 42, and 70 lb respectively, and is meant for use with molds 14” and larger (Slater doesn’t recommend an insert for 12”-and-under molds, suggesting a lightweight concrete mix instead for those).

The foam is built to withstand the heat generated as concrete cures, and Slater’s own installation video walks through drilling and centering the insert plus using concrete strengthening fibers and a high-strength mix (e.g. Quikrete 5000) to offset the added air cavity. Slater recommends leaving at least 4” of concrete on every side of the insert to reduce the risk of the finished stone cracking. No independent reviews of this accessory surfaced during research – coverage is limited to the manufacturer’s own listing and tutorial.

Type	foam lightening insert for DIY atlas stone molds
Material	high-density foam (heat-resistant during concrete cure)
Installation	embedded in concrete pour; keep 4"+ concrete on all sides to avoid cracking
Sizes available	6", 8", 10", 12"
Recommended concrete	high-strength mix (e.g. Quikrete 5000) with concrete strengthening fibers
Sold separately from	Slater Atlas Stone Molds (required to use this insert)
Weight reduction by size	6": ~10 lb, 8": ~25 lb, 10": ~42 lb, 12": ~70 lb
Minimum recommended mold size	14" (not recommended for 12"-and-under molds)

What is a Strongman?

Strongman equipment trains raw, functional strength through odd-object lifting, carrying, and loading — atlas stones, yokes, farmer’s handles, sleds, logs, and tires — rather than the fixed, balanced resistance of a barbell. It’s a fit for lifters who’ve plateaued on conventional strength training and want to build the grip, bracing, and full-body coordination that competition strongman and functional fitness demand, or who simply want the most direct training carryover to real-world lifting and carrying tasks. Most pieces are bulky and some (tires, natural stones) are sourced or repurposed rather than bought outright, so plan for storage space and, in a few cases, DIY sourcing as part of owning this equipment.

How it compares

	Slater Atlas Stone Lightening Insert	Natural Stone - Custom/DIY	APE FITNESS Workout Sandbags	Feed Sack
GymRadar rating	5.0/5	5.0/5	5.0/5	5.0/5
Price			$49.99
Type	foam lightening insert for DIY atlas stone molds
Material	high-density foam (heat-resistant during concrete cure)		1000D MIL-Spec Cordura shell (per manufacturer; a same-named Chinese OEM listing describes a similar bag as 1000D Nylon -- unresolved discrepancy)	1000D Domestic Cordura
Installation	embedded in concrete pour; keep 4"+ concrete on all sides to avoid cracking
Sizes available	6", 8", 10", 12"
Recommended concrete	high-strength mix (e.g. Quikrete 5000) with concrete strengthening fibers
Sold separately from	Slater Atlas Stone Molds (required to use this insert)
Weight reduction by size	6": ~10 lb, 8": ~25 lb, 10": ~42 lb, 12": ~70 lb
Minimum recommended mold size	14" (not recommended for 12"-and-under molds)

5.0/5 · 3 GymRadar reviews

Reviews by source

Expert

5.0/5

3 reviews

The Slater Atlas Stone Lightening Insert is a high-density foam core that mixes into the concrete pour for a Slater Atlas Stone mold, hollowing out an air pocket to shave 10-70 lb off a finished stone (depending on insert and mold size) without shrinking its overall dimensions. Independent editorial and community coverage of this specific accessory is essentially nonexistent – no expert review, Reddit thread, or third-party YouTube video turned up during research – so the verdict here leans heavily on GymRadar’s small owner sample and the manufacturer’s own installation guidance. Build quality is the standout dimension: GymRadar’s owner sample rates it a perfect 5/5 (n=3), and the manufacturer pairs the foam with clear instructions (4”+ concrete clearance, strengthening fibers, a high-strength mix) aimed at preventing the exact cracking risk a hollow-core stone introduces. Value is the weakest dimension to assess: at roughly $25 for the smallest size it’s cheap relative to a full stone mold purchase, but with no independent reviews to corroborate the glowing owner sample, that price-to-quality read is unverified.

+Build quality: high-density foam engineered to withstand the heat of concrete curing rather than degrading (manufacturer product page)
+Build quality: GymRadar's owner sample rates the product a perfect 5/5 across 3 reviews
+Functionality: reduces finished stone weight by roughly 10-70 lb depending on insert size (6"/8"/10"/12") without changing the stone's outer dimensions (manufacturer product page, installation video)
+Functionality: manufacturer's own installation video walks through drilling, centering, and pouring around the insert step by step (YouTube: Slater Strength)
+Value: low entry cost (from $24.99) relative to buying a heavier stone and separately trying to manage its weight

−Durability: no independent long-term reports exist on whether the hollow core holds up to repeated stone drops -- all guidance (4"+ clearance, strengthening fibers) is preventive advice from the manufacturer, not field-tested feedback
−Value: no independent editorial review, YouTube review, or Reddit discussion of this specific product surfaced anywhere in research -- the GymRadar 5/5 is the only third-party signal
−Versatility: not usable on its own -- requires a separately purchased Slater Atlas Stone mold, and the manufacturer advises against using it at all in molds 12" and under
−Value: the 6" size was listed sold out at research time and per-size pricing for the 8"/10"/12" variants wasn't shown on the manufacturer page