Bison moisture-absorber crystals, a 2.5 kilo refill at 12.00 euro: the maker says one kilo lasts three months, which is 1.60 euro a month

This is a Bison 2.5 kilo bag of loose moisture-absorbing crystals at 12.00 euro, rated 4.7 from 50 reviews, shown in stock with next-day delivery when ordered before 23:59. It is not a machine; it refills the plastic moisture trap you already own. The maker puts three usable numbers on the page: one kilo of crystals works for roughly three months in a space of up to about 100 cubic metres with little or no ventilation, one kilo absorbs around one litre of water, and the whole thing uses no energy and makes no sound. Once the Dutch autumn sets in, the room where the heating went off and the window cannot stay open is exactly where this bag earns its place.

• Quantity and duration: a 2.5 kilo loose refill; the maker states that one kilo works about three months in a space of up to roughly 100 cubic metres and absorbs about one litre of water per kilo filled. (source 1)
• No electricity: the page lists costs no energy and works silently as product properties, which is what separates it from an electric dehumidifier. (source 1)
• Where it is meant to go: the maker names caravans, boats, sheds, meter cupboards, attics, pantries, cellars, crawl spaces, guest rooms, wardrobes, garden houses, kitchen cupboards, safes and laundry rooms. (source 1)
• The precondition: it targets excess relative humidity in closed spaces with little or no ventilation, which the page states in its first sentence, so a room you can air out is not its use case. (source 1)
• Price and stock: 12.00 euro, rated 4.7 from 50 reviews, shown in stock with delivery tomorrow when ordered before 23:59. (source 1)
• Compatibility: the page states it suits all refillable moisture traps, so it does not have to match the brand of your existing tub. (source 1)
• The tub itself: Bison own Vochtvreter Original, tub plus 450 grams of crystals, is 10.49 euro and rated 4.8, which shows the common tub takes 450 grams rather than a full kilo. (source 2)

The sum is short: 2.5 kilos divided by however much your own tub takes gives the number of fills, and each fill times three months is how long the bag lasts. On the maker one-kilo figure that is two and a half fills, roughly seven and a half months, and 12.00 divided by 7.5 is 1.60 euro a month for one room. Cover two rooms at once and the time halves to 3.20 euro a month. Use your own tub capacity for this, because tubs take anywhere from 450 grams to a full kilo and that doubles or halves the answer.

The second number is worth more than the price: one kilo absorbs about one litre of water. That is not an abstract claim about performance, it is a quantity you can check. When the lower chamber is approaching a litre, that is the moment to refill, rather than refilling by the calendar. The maker also says the real result depends on temperature, humidity and the size of the room, so treat the litre as a reference rather than a guarantee.

The trade-off against an electric dehumidifier sits here. The crystals use no power at all and therefore have no running cost, but their throughput is measured as roughly a litre per three months, while a household electric dehumidifier pulls several litres in a day. They are not substitutes. Wardrobes, storage rooms, meter cupboards and cellars, the small unventilated places nobody sits in, are where crystals fit best; a whole living room or a persistently damp house is beyond them.

One precondition deserves stating plainly, because the page opens with it: this is for spaces with little or no ventilation. If you can throw the window open every day, do that first, because it is free. These crystals are for the corners where you cannot, and after the bedroom heating goes off in autumn, cold outside walls are where condensation shows up, which makes wardrobes and storage against an external wall the place to put one.

The bol link on this page is an affiliate link: the bag of crystals is still 12.00 euro if you order through it, and Hokimi may receive a small commission.

Price

12.00 euro

Rating

4.7 out of 5 from 50 reviews

Specs

2.5 kg loose refill・one kilo lasts about three months・absorbs about one litre per kilo・no electricity

Platform

bol.com, EAN 8710439200927

Checked

Listing read on 7 September 2026