These are smaller than I expected, but that is an asset because they will fit into just about any size footwear.They are very easy to use, and the operating instructions are easy to follow, however I was at first confused because the UV-C bulbs did not illuminate. I wondered if humans maybe cannot see 253.7 nm light, but there are pictures on the description page showing a blue glow. I started researching this issue and finally decided to write to the seller to ask if I should see a light or if my received item maybe was defective.At the ZEBEI page there are 61 different products to see. I did not end up writing to ask that question because I got an answer from a video there of some woman showing the shoe dryer/deodorizer. In that video she mentioned making sure the bulbs are screwed in completely. When I checked, sure enough, both bulbs were actually loose! It only took a moment to tighten them and suddenly there was a blue glow when I tried the deodorizer again!I also found a replacement UV-C bulb listed at the ZEBEI page. I had looked at the dryer/deodorizer product page wondering where to get a replacement bulb in case it stopped working. that ZEBEI page ended up answering two questions I had!I think there should be a reference to tighten the bulbs at the main page and also in the printed instructions. I read them twice when I was uncertain whether the UV-B lights were working but found no guidance or any reference. Glad I stumbled onto that video!I am now running another trial in a pair of shoes and the lights are indeed glowing inside the shoes. I like the flexibility to set many different times for operation and also that the UV-B light runs first, and the heat cycle will not begin until the UV-B cycle is finished.I cannot yet attest to the actual efficacy, but from my initial test with only heat there was a definite reduction in odor. Now with the UV Light I expect it to me even more effective. This is a clever device, and I am very glad to have sourced it!I already have a traditional boot dryer that runs hotter and can accommodate tall boots. The old unit is very effective at drying out wet boots, but this new one will do less damage from heat and theoretically sanitize with the UV.