Sight Plugs
Ldi Industries LSP151-08-01 Gage, Sight Plug, Lo PSI, Body: Solid Bras
Ford put extra effort into the sealing against dust.
Ldi Industries LSP51-09 Sight Plug Gage, NPT 2-11 1/2 Inches
What stands out about the 1620 is how it fits standard shelving units.