Indoors and away from water, unrated IP20 strip is fine and is the cheapest option. In a bathroom, or anywhere exposed to splashes and steam, you need a sealed strip rated for the zone it sits in. Outdoors you need a higher rating again, because the strip has to cope with driving rain rather than the occasional splash. We stock separate waterproof, bathroom and outdoor strip ranges, so filter by IP rating rather than assuming, and confirm the zone with your electrician if the run sits near a bath or shower.