Remarkable, wonderful Riemann P20 Sunfilter Riemann P20 Once-a-Day Sunfilter is a well tried and tested product to protect from sunburn while allowing a gentle, slow golden tan. It is a unique product as it needs to be applied only once a day - 90 minutes before exposure to the sun - so theres no need to re-apply the product - you can simply get on with enjoying yourself. (Easy-to-follow instructions are provided with each bottle). Riemann P20 Once-a-Day Sunfilter provides high sun protection - factor 20 - and is still 90% effective after swimming. P20 is fragrance free and non-greasy once dry. No grease and no shine make it ideal for women to use under make-up or for applying to the scalp. (It is often recommended by dermatologists to men with thinning hair).