Words from Rollei:

Rollei RPX 25 is a low-speed panchromatic black and white film with a nominal sensitivity of ISO 25/15°. Aside from the extraordinarily fine grain, the Rollei RPX 25 has great resolving power and high acutance. Rollei RPX 25 is characterized by a high sensitivity reserve of one f-stops, depending upon development. The thin, silver-rich emulsion is coated onto a crystal-clear base and offers an excellent balance between image quality (sharpness/fine grain) and speed yield.

Features:
• low-speed panchromatic film, ISO 25/15° 
• resolving power contrast 1000:1 = 260 lines/mm 
• RMS granularity (x1000) = 8 
• extended exposure latitude (between 12 and 50 ISO) 
• good for push/pull processing 
• good tone reproduction 
• great maximum density 
• transparent = ideal for scanning and as a slide 
• anti-curling layer ensures optimum flatness