YSI PRO20 Mode D'emploi page 31

Using alcohol on o-rings may cause a loss of elasticity and may
promote cracking.
Do not use a sharp object to remove the o-rings. Damage to the o-
ring or the groove may result.
Before re-installing the o-rings, make sure to use a clean workspace, clean hands,
and avoid contact with anything that may leave fibers on the o-ring or grooves.
Even a very small amount of contamination (hair, grit, etc.) may cause a leak.
To re-install the o-rings:
Place a small amount of o-ring grease between your thumb and index finger.
(More grease is NOT BETTER!)
Draw the o-ring through the grease while pressing the fingers together to place a
very light covering of grease to the o-ring. Place the o-ring into its groove making
sure that it does not twist or roll.
Use the previously grease-coated finger to once again lightly go over the mating
surface of the o-ring.
Do not over-grease the o-rings. The excess grease may collect grit
particles that can compromise the seal. Excess grease can also cause
the waterproofing capabilities of the o-ring to diminish, potentially
causing leaks. If excess grease is present, remove it using a lens cloth
or lint-free cloth.
27