This is the OEM Spacer and Shorter OEM Belt Nissan used to eliminate the idler pulley from pre August 2006+(later models already have this delete from the factory) model VQ35DE Engines. The Spacer is placed in between the engine and the power steering mounting bracket in the space the idler pulley bracket would be normally.
By eliminating the idler pulley you remove almost 1lb of rotating mass from the engine and eliminate a wearing part that will eventually fail anyway. The idler pulley and bracket together weigh almost 3lbs.
This kit comes with ONE Nissan alternator belt and ONE idler spacer and ONE A/C Belt (ALL NEW NEVER INSTALLED)
Bought this from Z1Motorsports for my 06 350z but recently traded it in so no longer need this. Save on shipping and conversion rate. Price is $40 firm. Don't throw me offers.
Nissan OEM Idler Pulley Elimination Kit
Check out diagram in the link.