There isn’t better way to store your leaders, especially if you want to store them fully rigged with tippet and a fly. At just 7mm thick, they are
Nirvana Fly Leader Rig Holder 4 Pack (Extra Thin)
NIRVANA Tenkara Line Holder Cards (6 pack) — DRAGONtail Tenkara
Loon Outdoors RIGGING FOAM (3 PACK) : Sports & Outdoors
Nirvana Tenkara Line Holder (4 Pack)
Nirvana theDRIFTER Floating Furled Dry Fly Leader (0-3wt) : Sports & Outdoors
Leader Holder
Nirvana Fly Leader Rig Holder 4 Pack (Extra Thin
NIRVANA On The Fly — Moonlit Fly Fishing
Nirvana Tenkara Line Holder Cards (6 Pack) : Sports
Nirvana Line Holders (4 pack) — DRAGONtail Tenkara
Nirvana Fly Leader Rig Holder 4 Pack (Extra Thin) : : Sports & Outdoors