These are a 6-rib design. If you need idlers I make these as well. If you'd like to upgrade to an 8 or 10 rib system and have a crankshaft pulley I can make you idler pulleys. These pulleys will allow you much more adjustability in your boost level.
8 Rib Magnuson Magnacharger TVS2300 / TVS1900 Supercharger Pulley
Magnuson Supercharger Pulley 6 Rib 3.700 Magnacharger 57-00-06-037
Magnuson Supercharger Pulley 6 Rib 3.800 Magnacharger 57-00-06-038
Magnuson Supercharger Pulley 6 Rib 3.600 Magnacharger 57-00-06-036
2.75" Magnacharger Radix Style 6 Rib Supercharger Pulley 04-09 Chevy & GMC Truck
2.60" Magnacharger Radix Style 6 Rib Supercharger Pulley - 2000-2006 Corvette