Oil restrictors replace the production oil galley plugs at the rear of the block and restrict oil flow to top end, forcing more oil to bearings and cutting power loss from windage, Sold in pairs with two extra O-Ring seals. Note: Not recommended for hydraulic lifter engines.Pit Stop USA offers Allstar Performance SB Chevy Oil Restrictors - .055" I.D. Hole- Aluminum w/ Hex Head. ALL90070 at low everyday prices. Be sure to check out all of our products from Allstar Performance including Allstar Performance Oil Restrictors.