They are based on the Japanese spec of the Saltiga reels, over there they only make the 10, 15 and 35 size all of which come with spool locks since they are jigging reels for their market. In the US the 10's and 15's retain the spool lock, and you can even buy 3 parts to change them over to auto-engage when you turn the handle since they are a good jigging size. The 20, 30, 35, 40 and 50 in the US all come with a centrifugal cast control instead. The spool locks are great for bottom fishing and jigging, and getting unsnagged on light action rods.