Theft protection during storage and transit. Does not need to be removed during use of the propeller. A free spinning collar will turn if attacked by gripping tools without loosening the lock. Constructed of naval brass and hardened stainless steel
options are
Mercury & Mariner over 70hp - nut thread 3/4" x 16
Mercruiser Alpha One - nut thread 3/4" x 16
Mercury & Mariner over 70hp - nut thread 3/4" x 16
Johnson & Evinrude over 140hp - nut thread 3/4" x 16
Johnson & Evinrude 40-140hp - nut thread 5/8" x 11
OMC king cobra - nut thread 3/4" x 16
Yamaha over 115hp - nut thread 18mm x 1.5
Volvo SX - nut thread 3/4" x 16