This is for 610-PO10, 610-PR10 and 600-PO10, 600-PR10 Series.

Straight Thru Hole, No Filter, 0.13 µL Volume, Pack of 5, goes with 610-4025 for 610 series and 600-0001 for 600 series Inlet filter housings.

If you see more back pressure than you expected, then we may try this. 

In general, the no filter option is for cases where absolute minimum dispersion is required, as the filter can add some amount of dispersion, and also for cases where another inlet filter is installed in a line.