Easton loves a challenge. And there's no bigger challange than improving on their hugely popular Full Metal Jacket arrow shaft. But they've done it by packing all the power of the original into a new 4MM micro diameter (.166" inside diameter) shaft. The FMJ 4MM will give you unmatched knockdown power! The Precision 7075 alloy jacket is bonded to a carbon core to provide minimal friction and extraordinary strength. Pair that with the included outserts for increased FOC. You'll get deeper penetration and increased likelihood of pass-throughs on even the toughest of big game. Features Straightness: ±0.002" Weight: ±2 grains 4MM micro diameter carbon-fiber core with 7075 aluminum metal jacket Increased kinetic energy Better penetration Lower friction 4MM MicroLite™ nocks are installed 4MM 8-32 aluminum half-out inserts (50 grains each) are included Sold by the 12-pack See all Easton products 4MM FMJ Carbon Shafting Specifics Deflection/Spine Point GPI Length Insert Nock 400 5/16" 9.8 31.5" 4MM Half-Out (50 gr) MicroLite 340 5/16" 11 32" 4MM Half-Out (50 gr) MicroLite 300 5/16" 11.7 32.5" 4MM Half-Out (50 gr) MicroLite 250 5/16" 12.3 33" 4MM Half-Out (50 gr) MicroLite Tolerances Straightness: ±.003" Weight: ±2 grains