Brilliant in a Lunch Bag, Out of Their Depth in a Cool Box: G4GADGET Freezer Blocks

Slim is a feature, not a flaw (if you pack a lunch bag)

Let's start with the people who give these five stars, because there are a lot of them. In the recent sample, 61 of the 100 reviewers left top marks, and a clear pattern runs through their comments: these blocks fit where chunky ones won't.

Lucy-anne bought them specifically for lunchbox-sized cool bags and called them "the perfect size for lunchbox." Verrol Jones liked the "great thin design, fits snugly in my lunch box." Susan Layden summed up the appeal: "quite thin so don't take up loads of room ... ideal for cool bags." If you've ever tried to wedge a fat supermarket ice block into a slim insulated lunch bag and then failed to zip it shut, you'll understand instantly why the thinness gets praised.

One reviewer, Amazon Customer, mentioned the blocks were "small enough that I can still close the lunch box with no issues" and kept their kids' food cold right through to the school pickup. For packed lunches, day trips and keeping a salad from going warm by midday, this is exactly the use case the design was built for.

Load a full cool box and the cracks start to show

Now the other camp. The reviewers who wanted these for a proper cool box, the kind you'd take camping or leave in the boot on a hot day, tend to come away underwhelmed, and again it's the slimness driving it.

Jade kept it short: "Does not stay cold for long." Alasdair, who half-blamed his own kit in his review header ("Maybe my coolbag is too big for these"), said they "doesn't keep things as cool for as long as I would like." McShaney found a workaround, ending up using two blocks at a time in one cool bag rather than relying on a single one. That's the trade-off in plain terms: less ice mass means less staying power. A thin block freezes fast and thaws fast.

For a typical UK weekend camp, where you might want milk, sausages and a few cans holding their chill from Friday night through Saturday, these alone won't cut it. They'll help, but they're a supporting act, not the main cooling source. If a long hold time in a big box is your priority, a thicker dedicated cool-box brick is the better spend.

The listing photo is causing most of the one-star reviews

Here's the single biggest source of frustration, and it has almost nothing to do with how the blocks perform. The product photo and the "assorted colours" wording lead a lot of buyers to expect something they don't receive.

Two complaints come up again and again in the recent reviews. First, the colours. The listing suggests assorted colours, but a large number of buyers report receiving all blue (or clear with blue liquid inside). Darren Sowerby: "It says assorted colours but yet all clear with blue liquid." Gwen ordered the assorted four-pack and "all 4 came clear with some blue liquid inside." One reviewer, Mrs K. C. A. Dallimore, was specifically annoyed because she already owned blue ones and ordered these for variety, only to get more blue.

Second, the count. Several buyers say the main image appears to show six blocks when you actually get four. Mrs Debbie Holland called it a "good product but misleading photo shows pack of 6 but actually only a pack of 4," and Emma Bonney pointed out that the text does say four even if the picture suggests otherwise. The product is, to be clear, a pack of 4. The blocks measure 16cm. Neither of those facts is hidden in the listing text, but the imagery sets a different expectation, and that mismatch is what tips otherwise-functional purchases into one and two-star territory.

The takeaway: buy these expecting four slim blue blocks, and most of the disappointment evaporates before it starts.

Build quality: mostly fine, occasionally thin enough to worry

The plastic is light, and a few reviewers flagged it. Pauline Clark warned the "very thin plastic easy to put a hole in," and Mrs Chicken noticed "a particularly thin area on one of them" she worried might burst. A couple of buyers had blocks arrive cracked or leaking in the post, including Tope, who got two of four damaged on delivery.

That said, plenty of long-term users report no such trouble. Amy said hers "feel sturdy and haven't leaked or cracked." Purplebe4n had "no leaks or issues so far." One Amazon Customer had used theirs often over a long stretch and reckoned they were "still as good as the day I got them." Starry Night was initially nervous about the blocks bulging in the middle when frozen, but after several uses concluded the plastic had "enough give" to expand without splitting.

So the picture is mixed but lands on the reassuring side: most are fine for repeated use, a minority are flimsy or arrive damaged. At this price you're not expecting heavy-duty hard-shell construction, and you're not getting it. Treat them gently, don't over-stuff the cool bag, and they tend to last.

The clever off-label uses campers will appreciate

One of the nicer surprises in the reviews is how many people use these for things that have nothing to do with sandwiches. The slim, freeze-fast design turns out to be handy well beyond the cool bag.

Mumma JoJo keeps baby food and medication cold on the move, noting the blocks "pop nicely into any lunchbox, changing bag or small medical bag" which is a really useful tip if you're travelling with little ones. Another buyer, Myreviews0147, bought them for wisdom tooth pain but ended up using one on a twisted ankle as a quick cold pack. Starry Night even tucked one under a towel to help keep the family dog cool during a heatwave, which UK summers increasingly call for.

For campers, the lesson is flexibility. These aren't just for the food box. Stash a couple in the freezer and they double as first-aid cold packs, kid-soothers and emergency chillers without taking up much room. That versatility is a quiet point in their favour.

So should you buy them?

It comes down to one question: what are you cooling, and how big is the bag?

If you want slim blocks for a lunch bag, a small cool bag, packed lunches or days out, these are an easy recommendation at £5.99. They freeze quickly, fit where bulkier blocks can't, and a strong majority of buyers are happy with them for exactly that. Pauline used hers in a cool box on a four-hour holiday drive and "they kept everything cold," so they're not hopeless in larger setups either, just not your only line of defence.

If you're filling a full camping cool box and need things cold from one day to the next, set your expectations accordingly. Buy a few packs and double up, or pair them with a thicker brick. On their own in a big box, the thin profile means a shorter hold.

And whatever you do, go in knowing you'll get four slim blue blocks. Do that, and the most common reason people leave a low rating simply won't apply to you. For a fiver, as a flexible bit of cooling that lives permanently in the freezer door, they're a sensible buy.