Panasonic PT-LB355U Operating Instructions Manual page 113

Chapter 7 Appendix - Ceiling mount bracket safeguards
rDimensions for the screw holes to fix the projector (projector bottom view)
Unit: mm (inch)
23 (29/32")
105 (4-1/8")
140 (5-1/2")
260 (10-1/4")
ENGLISH - 113