I cycle in the dark a lot (as we all do these winter months) and I am always looking for stuff to make myself a little more visible to other road users. Well, these little babies don't half work! Clipped to each spoke on my front wheel, I now look a little like something out of Close Encounters and was tailed by a couple of Tornado jets for several miles the other day (I jest). Bear in mind that they principally provide visibility from the side, so they /compliment/ a good set of bike lights. They do NOT remove the need for lights.
They attach easily and are very secure - I have ridden many miles off road this year with them attached and I haven't lost a single one.
Pay a little more and you can buy enough to fit them to both wheels.
UPDATE
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Now the dark mornings/dark evenings season is ending and we can look forward to months of daylight cycling I can report that, happily, I haven't been run off the road once (yet)! These spoke clips obviously work!