MONO Smart Eraser / Tombow

• Model: ET-ST
• Dimensions: W67 × H17 × D6 mm
• Thickness: 5.5 mm
• Eraser Material: Elastomer
• Sleeve Material: Recycled paper (50% or more recycled paper pulp by mass)
• Eco Compliance: Green Purchasing Law compliant
• Phthalate Ester: Free
• Awards: Good Design Award 2013, iF Design Award 2014

The MONO Smart Eraser grew out of a specific frustration: standard erasers are too thick to target a single ruled line. A/B ruled notebooks use a line spacing of roughly 7mm, and a typical eraser body sits well above that, making precise single-line corrections nearly impossible without smudging adjacent text.

Tombow's response was to engineer an eraser body at 5.5mm, just under that line spacing, so the erasing edge sits cleanly within one ruled line. The challenge was that making an eraser that thin typically means making it flexible, which reduces control and causes uneven correction. Tombow developed a dedicated elastomer compound that holds its shape under the pressure of normal erasing, keeping the edge true even when bearing down on fine detail work.

The sleeve adds another considered detail: the corners are cut in a U-shape so the eraser body doesn't catch and dig into the paper sleeve when you push down. The sleeve itself is made from recycled paper pulp, qualifying the product under Japan's Green Purchasing Law. The MONO Smart Eraser won both the Good Design Award in 2013 and the iF Design Award in 2014, recognizing the engineering behind what looks, on the surface, like a simple thin eraser.