Skin rather than strength is what the Zenlabs pair covers: Tretizen 10 and Tretizen 20, one line in two strengths, at 4.90 and 7.20. Both are in stock and both sit with the dermatological items the shop keeps.
Two listings is the entire label here, so the page functions as a choice of strength rather than as a catalogue. They are also among the cheapest entries anywhere on the site, which tends to put them into orders assembled around something else entirely.
