Yup. Doesn't really exist in american pot culture, though - from that point of view, it is a filter. I think some folks would call those rolled-up paper bits wussy or something. Then again, lots of folks here (Norway) smoke hand-rolled cigarettes without filters as well - mostly starts as a cost-saving thing and cops aren't going to give you crap for having drug paraphernalia because you have cigarette papers like they would in the states.

I can't remember if I've seen actual filters for sale in the shops in Amsterdam or not, but I'm going to guess they'd sell so long as they don't affect the buzz at all.