This is Loctite 55 Pipe Sealing Cord by Henkel.
What it’s used for:
Sealing threaded pipe joints so they don’t leak. It’s the modern alternative to PTFE tape + pipe dope.
Key details from your container:
1. Product: Loctite 55 PIPE SEALING CORD - white fiber cord impregnated with sealing compound
2. Approved for:
• Cold and hot water up to 130°C
• Potable water = safe for drinking water lines
• Gas = natural gas, LPG, etc.
3. How it works: You wind the cord into the male thread grooves. When you tighten the fitting, it swells and fills all the gaps to make a leak-proof seal.