Product review (2 stars): The stem was made too skinny.
I wish I had read P. Cwik's review before I purchased it.  It was exactly what happened to me:  it falls out of the grate when you flip it. It is GE's WB02T10461 Profile gas range. The stem is simply too thin. Considering the price, only around $9 for 8, I don't feel a total loser, and I didn't bother to return it. I think I will just carefully put them aside every time when I clean the grate.
The delivery was quick. It took only 2.5 days. That is the one of the best I had ever experienced.