I used those light for decades. They work very well. Car driver response is excellent. I find cars in general giver me more clearance with those than with far brighter flashers that are stationary on me or the bike.

Several comments. 1) thankfully much lighter and more comfortable options exist now. At high pedaling RPMs the ankle takes a real beating with those 2 C-cell batteries. And, thank you, DuraCell and alkaline batteries and now better! The pre-alkaline days of lead batteries meant a lot of rides home in the dark..

2) For less bone battering and also visibility in front of panniers, strap the light below your knee. Same vertical movement effect, very little pannier screening. (I never rode with rear panniers so that simply wasn't an issue for me but the constant bone bruising on my ankle was.)