That "pylon" kind of looks like the FLIR component of a targeting or navigation pod. We can see the forward facing aperture that would be consistent with a FLIR for navigation purposes, and we can also see that the pylon itself is bulkier than a normal weapons pylon yet it is also intended to clearly carry some kind of object below it.I must admit, I'm not entirely sure - esp. since that image is too blurred - but could be that these J-16s featuring the new light-grey coloured radome are indeed already Block 5 aircraft?
It seems a bit as if the construction number on this J-16 is '0502' ... and also, I never noticed this detail on the pylon's front.
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Many targeting or navigation pods have a FLIR component as part of the "pylon" which carries the pod.
For example, the AN/AAQ-13 navigation pod. The AN/AAQ-13 is separated into two halves; the "top" half is a FLIR, while the bottom pod half is the terrain following radar.
Various other targeting pods have similar arrangements where the "pylon" is a forward looking FLIR, and the actual pod component houses the main sensors.
For example, the damocles, ATFLIR and J/AAQ-2 have a similar arrangement.
For J-16, I would expect that pylon/FLIR to accommodate a targeting pod rather than a navigation pod, given few aircraft these days have dedicated terrain following radar pods like the F-15E (whose solution was elegant and capable but which most recent fighters have the ability to use onboard radar for terrain following)