Headset ABEC 3 angular contact ball bearing with 40 mm inner diameter, 52 mm outer diameter, 6.5 mm thickness and double-lip type sealing.
36x45° Cane-Creek-Standard. 
Enduro Bearings don't mess around with inexpensive headset bearings, it's simply not worth it. While many headset makers will offer you Cr-Mo or standard steel headsets for your carbon road bike, steel cross bike, or full suspension mountain bike, they feel that's like putting bias ply tires on a rally car. Enduro Bearings don't offer the entry level for headset bearings. Instead they begin with chromium steel, Black Oxide finish A/C type and then offer full 440C stainless steel at the top. They are always engineered with the largest balls possible and dual lip seals riding in a micro groove for ultimate protection against sweat and the elements. They are filled 90% with high pressure water proof grease, so you don't have to ever guess if there is grease inside. 
In standard radial bearings, only 3 or 4 balls make contact during the load, at any given time. In Angular Contact (A/C) bearings, ALL balls are engaged and spread the force over a larger surface area, to decrease friction and minimize wear. 
ABEC 3 bearings use grade 10 Chromium Steel Balls and 52100 High Carbon Chromium Alloy Races.
The high precision balls are within 10/1.000.000″ round, twice as round as the industry standard, at it's highest level. 
The alloy races are made from a vacuum de-gassed process for the purest chromium alloy steel, hardened to R-62, extremely tough and very durable. Polished to a mirror finish for ABEC-3 precision and noiseless movement. The riveted Steel Retainer stands for toughness, ABEC-3 tolerances and noise tested.
Manufacturer item code: ACB 6808 CC BO
| Product name: | Enduro Bearings ACB6808 CC BO - ABEC 3 - Headset Angular Contact Ball Bearing - 40x52x6.5mm (36x45º) | 
| Manufacturer: | Enduro Bearings | 
| Item code: | ENO280392 | 
| Activity: | Cycling | 
| Bearings type: | Angular Bearing, Ball Bearing, for Headsets | 
| Bearings inner ø: | 40 mm, 1 1/2" | 
| Bearings outer ø: | 52 mm | 
| Bearings width: | 6.5mm | 
| Bearings static load: | 5858.4N | 
| Bearing material: | Chrome Steel | 
| Weight: | 25g | 
| Manufacturer page: | http://endurobearings.com/ |