The long leather strap is the 250-day membership reward. It is capable of carrying 14 weapons, which is 4 greater than a regular leather strap. It also looks longer when in a player's inventory, and is one pixel longer on both sides when on the ground.
Sholop sells the long strap for 1000 gold and will buy it for 167 gold, while Darklow will sell it for 1105 gold and buy it for 134 gold. Tavelor charges 248 gold to engrave it.