The EXT Ferro Fork Requires a Hub boost spacer for your Brake Rotor, check that box if you don't already have one.   If you have 18/21 in wheel set you must get a drop crown. We also recommend a drop crown for most other bikes and tire sizes. it gives you much more adjustment.   At EXT Racing Shox, the research and development of new technologies neverstops. They are focused on progress, bringing the best solution to the market withthe aim to satisfy the needs of the most demanding riders. Since the growing worldwide success of electric dirt bikes, we saw theopportunity to take our extraordinary decades-long know-how on dampers, implementing a new custom solution to achieve the highest performance products for our customers. Something that brings your E-MX to the next level! EXT Racing Shox is extremely proud to introduce the brand new FERRO USD 36,an upside-down 36mm stanchion fork which is going to complete our E-MXline-up. Hard heat-treated chrome moly steel stanchions (Superfinish surface treatment),7000 series aluminum construction upper legs and a 205mm travel designwith a dedicated triple clamp, make the core of the new 36mm USD fork,developed for minimum friction and high stiffness. Together with the popular ARMA MX, already known for its industry leadingreliability and performance, you can now have access tothe best upgrade suspensions package on the market, purposelybuilt to boost the performance of your electric dirt-bike. Bike Fitment: Surron Light Bee E-Ride Pro SS Talaria Sting mx3 Talaria sting mx4 Talaria XXX Rerode R1 Throne Srpnt   CORE FEATURES Robust dual crown inverted MX design (USD) 36mm Ø hard chromed steel stanchions (heat treated 42CrMo4) with Superfinish surface treatment HS3 3- twin positive air system ¬+ 1 large negative self-balancing air chamber, allows for an optimum level of support through all the travel High flow 3-way cartridge damper system with independent high & low speed compression plus rebound damping adjustment. Superfinish inner tube coating External pressure air release system on both legs Twin hexagonal floating axle, boost compatible ∅20mm Air spring and cartridge radial guide system with bespoke aeronautical seals (minimize friction on side loads) Large piston design for best damping control and separate IFP/coil energized compression valve No cavitation and low hysteresis Self-hydraulic cartridge bleeding Dedicated Mobile Sliding DU guiding system with super-long static overlap (for maximum guidance and best torsional rigidity). (CGB Continuously Guided Bushing system, increase stiffness) 205 mm of travel and 44 mm offset 200 mm post mount brake Weight 4000gr Pressure release one-way valves on both legs Compatible with stock fender design  Boost Hub Spacing for more flexibility with after market wheel sets. HS3 The FERRO USD 36 fork uses the HS3 technology, the unique hybridair spring system, already been famous with the appreciated ERA V2.Two separate positive air chambers work with one, high volumeself-equalizing negative air chamber; HS3 is focused on mid-strokesupport around the dynamic sag position while offering amazingsensitivity and bottom-out protection Fork Structure Dual Crown Structure: The robust double crown design in 7075 aluminum ensures maximum stiffness. Crown design is compatible with stock fender designs.  Sliding Bushings:  We looked at everything that needed a low friction solution to improve smoothness and sensitivity. This process took us back to our 14 World Rally Championship wins, that make EXT the most succesful suspension manufacturer in WRC. Our new DU bushing material used in the new FERRO USD 36 fork are sized to a defined tolerances for each fork assembly and works in harmony with our dedicated EXT oil. This guarantees zero stiction and super low friction properties even when combined with high side loads.The dedicated DU guiding system made with a specific superlong bushing overlap ensures the maximum guidance and the best torsional rigidity of the stanchions. (We’ve called it, CGB, Continuously Guided Bushing system which also helps to increase thedynamic stiffness). Wheel Axle: Twin hexagonal head floating wheel axle guarantees perfect wheel alignment, while assuring maximum torsional rigidity. High Flow Damper Cartridge  The new FERRO USD 36 inherits the best technologies that made famous our well-known ERA V2 and it adopts an innovative radial floating shaft guide in the damper cartridge with a Super finish surface treatment with new aeronautical seals, which takes the friction to the lowest possible level. EXT high-volume cartridge uses a high flow piston to generate control for your bike, an important performance upgrade for your riding. The large piston design allows the best damping control. The cartridge is also equipped with a bump valve design (HDRV – High Dynamic Response Valve) with 2 different shim stacks for mid and high speed and an Internal Floating Piston (IFP) guided and combined with a bespoke thrust bearing to enhance fast response and guidance. Our goal has always been to find a balance between all the internal cartridge pressures and through a long development process we made possible the optimization of the internal forces reaching low values of hysteresis and no cavitation.  Note 1: For the Sur Ron if you are not on the most current model a head tube reinforcement clamp is recommended. This item is standard equipment on the current model year bikes. We have them available for purchase on our accessories page. Note 2:  Frame Bumpers from stock your forks will work on the EXT forks.