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Extralite UltraBottom Headset Lower Assembly

This is our new lineup of modular headsets. Extremely light and easy to configure on virtually any frameset. Just measure upper + lower headtube bore diameter then find your model on the chart.



HD (Heavy Duty) versions features 2 stainless bidirectional bearing cartridges that can handle double crown forks and manage Freeride abuses. Stainless and fully serviceable.

Improvements are on every single element of our original headsets, our new headsets are slimmer, lighter and trickier: a real concentrate of Extralite's high-quality engineering.

Reduced vertical dimensions allow more efficient bike layouts, as example you can use a longer travel fork while keeping your actual bar and BB level.

Japanese MX technology shows how to divide upper bearing (micro-radial) and lower bearing (stainless, bidirectional) steering functions; an ultra tricky layout that reduces weight and improves your race trim shrinking headset stack height.

Consistent weight reduction even if out of sight!

Model Head tube bore Tolerance SHIS Weight Headset style Fork standard Stack Height
UltraBottom 34 34mm 33.90-33.95mm EC34/30 30.3g Press Fit - External Cup Straight Fork 1-1/8” 9.5mm
UltraBottom 41 41 to 42mm 41.00-42.50mm IS41/30 or IS42/30 19.9g Integrated - Bottom Straight Fork 1-1/8” 1mm
UltraBottom 44 44mm 43.95-44.00mm ZS44/30 23.8g. Press Fit - Internal Cup Straight Fork 1-1/8” 1.8mm
UltraBottom 44 T 44mm 43.95-44.00mm EC44/40 38.3g Press Fit - External Cup Tapered Fork 1-1/8”-1.5” 10mm
UltraBottom 51 51 to 52mm 51.00-52.50mm IS51/40 or IS52/40 25.3g Integrated - Bottom Tapered Fork 1-1/8”-1.5” 1mm
UltraBottom 55 55mm 54.90-55.00mm ZS55/40 31.6g Press Fit - Internal Cup Tapered Fork 1-1/8”-1.5” 2mm
UltraBottom 56 56mm 55.90-56.00mm ZS56/40 32.3g Press Fit - Internal Cup Tapered Fork 1-1/8”-1.5” 2mm