I've found that there can be considerable variability between individual filters from the same shipment since they're hand assembled.
I tested a batch of 10 filters back in late 2010 from an incoming shipment that demonstrates the variability. From that batch, one filter only attenuated 108 MHz by 10 dB, another by 35 dB. The majority were between 15 and 22 or so.
Here's a single RS 15-0024 that I tested back in Nov 2013. It's the only one I tested.
