Review on Saugwunder Super Absorbent Cleaning Sponge - Durable, Water Resistant - 17.5×7.5×3.5 cm (6.9 x 3 x 1.38 inches) - Versatile Household Cleaner for Cars, Boats, Furniture, Bathtubs & More (Blue) by Chris Drury

I bought this sponge hoping it would last a long time. This works fine for my purpose. I had to make humidifiers for my harp case as I live in the desert. I cut the sponge into 5 long pieces. Then I bought five long plastic toothbrush holders. I drilled four holes in the top of each holder, put a piece of sponge in them and soaked them for a long time. Shake out excess water, dry outside and place in the harp case with the harp. They stay moist for two to four weeks. Works great and protects my harp and ukulele from drying out.