I spent seven years supervising an optical instruments engineering team and did a lot of work with glass bonding. My expectations for this product were, therefore, rather high.
The product is an anaerobic and UV-curable resin, suitable for stone chips and small cracks. When cured it seems smooth and perfectly clear. Both my applications were stone chips where a small section of glass (a little smaller than pencil eraser) was chipped out. The filled in section is completely invisible now. The resin filled in larger cracks as well. Very tiny cracks, however, won’t allow the resin to wick in and remain visible.