Bajaj built the Pulsar RS200 around the same airbox design used on the Dominar 400, and K&N engineers the BA-3717 as a single fitment across both. The layered cotton gauze media is oiled so airborne particles stick to it as air passes through, giving more airflow than the restrictive stock paper element while still catching dust and debris effectively.
The filter is washable and reusable rather than disposable, so instead of buying a replacement every service interval, you clean and re-oil the same filter and reinstall it using K&N's cleaning kit. The BA-3717 is backed by K&N's 10-Year/Million Mile Limited Warranty.