FLYPROFiber- 5dB SC Attenuator, Single Mode Fixed Fiber Optic Attenuator, Male to Female, 2pack

I work in the telecom industry. Are there higher quality attenuators than these? Yes. Do they cost a lot more? Also, yes.I measured these against a benchmark, and found one attenuator at 9.64dB and the other at 10.2dB (1310nm). That's not too far off, and well within acceptable tolerance for most users. It might have been nice if the range on two random attenuators was a little bit less (maybe within 0.2dB of each other), but optical polishing is still challenging to get consistent. In fact, this is where much of the expense of higher quality optical devices goes to...making consistent quality, or hand-matching specs, etc.For my needs, to attenuate power into an optical meter, these are just fine. I imagine if you could justify buying two or three sets, you would be able to match two specific attenuators quite closely. If I needed more, I'd certainly consider these again.