Premium PTFE Tape for Gas Fittings - 12mm x 5m - (1/2") Gas Pipe Plumbing BS21 Thread Sealant - High Quality Single Roll by Gocableties. 4.7 out of 5 stars. 481. £2.29. £2. . 29. Get it Wednesday, Jun 30. FREE Delivery on your first order shipped by Amazon.