1998-2000 for Yamaha YZ 125 MOOSE RACING Motor Gasket Kit with Seal 811637MSE they are simply different shapes

they are simply different shapes

Feature 6061 billet end caps and collars

Size: 15x6x6

Black vinyl/stainless kits include wire extensions

Drain and ventilation holes provide air circulation and easy cleaning

1998-2000 for Yamaha YZ 125 MOOSE RACING Motor Gasket Kit with Seal 811637MSE they are simply different shapesManufacturer: Moose Racing MPN: M811637 Title: Complete Gasket Kit with Oil Seals Size: Option: Color: Moose can now handle all your gasket and seal needs at a fraction of OEM cost High tech materials provide unmatched reliability and performance Rebuild the engine and transmission with total confidence as each set is designed for durability and accurate fit Oil seals are genuine OEM replacement seals All gaskets made in the U. S. A. STANDARD HIGH