Looks to be either a 5B or a 5Jr. Based on the apparent cabinet size, I believe it's the latter.
Monitor 5(B)
http://www.polkaudio.com/homeaudio/products/recent/monitor5/
Monitor "5jr+" http://www.polkaudio.com/homeaudio/products/recent/monitor5jr/
I've got most of the family--Monitor 5jr (sans PR), 5, 7, and 10. they are all high value/low price items. Still waiting for some 12's to pop up...
There was a "5" variant with a cabinet larger than any of the 4s but no PR (ported instead).
Looks to be either a 5B or a 5Jr. Based on the apparent cabinet size, I believe it's the latter.
how could his be 5 Jrs when the jrs have a PR that's the same size as the woofer, and his picture clearly shows a PR that's larger than the woofer?
it's either monitor 5 or some other monitor, not a monitor 5 jr.
If that's an 8" passive radiator, then yes, Monitor 5.
The Monitor 5 Jr. had a 6.5" passive radiator,
Regards,
Gordon.