This is a topic that requires some nuance and technical explanation. As such, we'll give a shorter and longer explanation, but we encourage you to read in full if you're concerned about flickering.
In short, our C7, C9, and S14 bulbs are fully-rectified, but do technically flicker. However, we're happy to report that for the vast majority of our customers, there is little to no reported perceptible flicker with our bulbs and many customers who have been sensitive to big-box store LEDs find no problems with our bulbs.
The longer version is that all light bulbs operating on a modern electrical grid's alternating current (AC) infrastructure are cycling on and off 50-60 times per second (measured in hertz).
This is true for even incandescent bulbs. With incandescent bulbs, however, the tungsten (or other filament material) stays hot enough between these cycles that it doesn't have time to dim between oscillations.
With LED bulbs, the diode has time to fully "turn off" in between these cycles, and this causes more noticeable flicker to the naked eye, since LED have no persistence like an incandescent filament.
Many cheap commercial LED Christmas lights are half-rectified, cycling at 60 hertz (in the US) but Tru-Tone bulbs are fully-rectified, meaning they cycle at twice that frequency – 120 hertz – and thus are "on" twice as often (or "off" for half the time) as half-rectified bulbs.
Perception of high frequency flicker is somewhat unique to each of us, and is usually noticeable only though peripheral motion such as when you move a light string quickly, or move your head quickly, catching them out of the corner of your eye.
If you find yourself in the group of unlucky individuals where any amount of flickering is bothersome to you, you may be interested in our DC-operated Mini Lites, which are 100% flicker free.