Sprint Filter P037 Air Filter for WorldSBK Racing – Ducati Monster 821 (2019–2020) R61S-WP-SBK

It is worth defining water-repellent by what it does not mean, because the phrase invites more than it promises. It is not a snorkel and it does not make an airbox waterproof; it is no licence to ride through standing water; and it changes nothing about where the Monster 821 draws its air from. What it describes is a property of the cloth itself: the weave sheds water rather than taking it up and holding it. That is a narrow claim, and narrow claims are the useful kind.

Key Features

• Water-repellent woven polyester, used dry, rated at 37 microns
• Rated throughput of 4,500 litres per square metre per second
• Carried in a carbon fibre frame, which is unaffected by repeated washing
• Roughly double the filtering surface of other performance filters
• Occupies the series panel position: nothing cut, no remap, ducting untouched
• Washable and reusable, warranted for two years from the date of purchase

Why a wet element is its own problem

An element that has absorbed water is restricting differently from the one that went in dry, and it does so while the machine is being ridden, at the point in the day when the weather is least helpful. That is the failure this grade addresses, and on an unfaired roadster it is not an exotic scenario: the rider decides in the morning whether to go out, and the motorcycle then takes whatever the afternoon does. The gain is a resistance that holds where it was measured. It is not a gain in output — nothing dropped into a standard airbox makes a Monster 821 stronger.

Reading the retention figure correctly

Sprint Filter publishes 91.8 per cent for this grade, and the number has to be kept in its own frame. It was arrived at with 37 micron particles; the 93.13 per cent quoted for the standard weave came from a test with 100 micron ones. Those are two experiments, not two places on one scale, and subtracting one from the other produces nothing. What does compare is the specification: 37 microns against 80, and 4,500 litres per square metre per second against 5,050.

Care and cleaning

Air first, on the clean face of the R61S-WP-SBK and directed outwards, which settles most of it. Water where air is not enough — hand-warm, a little mild detergent, rinsed until it runs clear; the repellent weave is washed like any other and takes no harm from it. Drying happens in circulating air alone, with no heat and no flame anywhere near the cloth, and the element goes back in dry and untreated. The maintenance sheet sits in the Downloads tab.

Fitment & Compatibility

Listed for the Ducati Monster 821 of 2019 and 2020. This kit number covers two machines altogether, the other being the Monster 1200 R of 2016 to 2019; both appear in the Fitment tab.