Emerson Copeland YB56K1G Application Manuallines page 32

If an oil regulator is used the oil level should be set within the top half of the oil regulator sight glass.
BOM versions GCY, JCD and 9J3 contain a stub tube connection 1 3/8" (35.3 mm) for paralleling on
the compressor housing at oil level height.
AGL_Ref_ST_YBK1G_EN_Rev01 27