NBR O-ring set for your filling probe, PR900 / P15 / P35.

Slips on easily, just use an o-ring pick and work carefully to remove the old O-rings if need be.

Clean out the grooves where the O-rings would sit in w/ a nylon bottle brush or old tooth brush to remove residue - Spray off w/ BALLISTOL UNIVERSAL OIL if need be.

Apply either silicone grease or rubber grease to the O-rings, then use your O-ring pick to fit them on - don't roll the O-rings over the probe, rather, work around the circumference and advance the O-ring bit by bit toward the groove. Fit the frontal groove first, then then second one, using, in the case of the second, the first fitted o-ring as a stepping block to get the (second) o-ring across.

Be sure to keep your o-rings lubricated. You can use silicone aerosol too if you want, it works just as good. Just watch out that the filling port doesn't nip your O-ring, due to said being dry - you'll almost guarentee yourself a leak via that damaged o-ring.

Dimensions are as per illustrated, supplied as a set / 2x O-rings. Filling probe shown for illustration purposes, not included in this deal, but sold separately.