The 3" Double Sided Seam & the 6" One-Sided Cover Tape is used by pond professionals to seam multible pieces of EPDM Liner together. We recommend using the Aquascape Designs Tape Primer (sold separately) to clean and prepare all surfaces before using the Seam & Cover Tape. For a more secure waterproof seam, use the 3" Two-Sided Seam Tape first, and then put down the 6" Cover Tape. Both tapes are available in 25" lengths and 100" lengths.