OE have this sturdy dual purpose leash for longboard and Stand Up paddle. 

Wave Size: SUP: 5ft (1.5m) – Longboard: 8ft (2.4m)

Cord: 8mm (1/3″)

Strap: 50mm

Features:

• ADVANCED MOULDED DESIGN – Advanced mould design with flex diamonds provides controlled flex. Designed to stretch with the urethane cord.
• DIAMOND FLEX MOULD – Advanced mould design with flex diamonds. Provides controlled flex and strong transition from mould to urethane.
• ORIGINAL DETACHABLE RAILSAVER – The original railsaver system designed by O&E, with a sewn-in anchor cord. Protects rails and is easily detached.
• 8MM DUAL ANCHOR SWIVELS – Marine grade, stainless anti-corrosive free-spin swivels for tangle-free surfing.
• CONTROLLED-STRETCH URETHANE – Premium grade quality urethane developed by the world’s leading manufacturer.
• FLEX NECK STRAP PLUG Allows 360 ̊ movement of the leash and offers more comfort when the leash is under load.