Arrow Thunder Aluminium Slip-On Silencer KTM RC 390 (2017-2020) 71860AK

The Arrow Thunder 71860AK is a road-legal slip-on silencer engineered for everyday riders who want a genuine upgrade without compromise. Weighing just 2.03 kg and carrying a full E-number type approval, it slots neatly into the daily commute or weekend canyon run while noticeably sharpening throttle response on the KTM RC 390.

Key Features

• Lightweight aluminium canister at 2.03 kg keeps unsprung mass low and improves throttle response
• E-number road approval means no MOT worries or insurance headaches — ride it straight from the box
• Integrated DB killer keeps sound levels within legal limits for everyday street use, removable for track days
• Carbon end cap adds a motorsport finish without the full-carbon price premium
• Stainless steel internals resist heat and corrosion for long-term reliability
• Can be paired with an Arrow header to form a full exhaust system for further gains

Build Quality

Arrow has constructed the Thunder canister from aerospace-grade aluminium, a material chosen for its combination of rigidity and low weight rather than simple cost-cutting. The 270 mm body handles the thermal cycling of spirited street riding without warping or discolouring. Internal components are fabricated from stainless steel, ensuring consistent flow characteristics and resistance to the condensation that shortens the life of cheaper alternatives. The carbon end cap is not a cosmetic stick-on but a structural part of the outlet assembly, adding durability where heat and vibration are at their most intense.

Performance on the Road

With a 54 mm inlet diameter and a 50 mm outlet, the Thunder is sized to complement the RC 390 single-cylinder's natural power band rather than simply evacuate exhaust gases faster. The result is a broader spread of mid-range torque that suits real-world riding — overtaking on A-roads, filtering in traffic, and carrying corner speed on track days alike. The DB killer ships fitted as standard, satisfying noise regulations without permanently strangling the exhaust note; removing it for private track use takes minutes.

Fitment & Compatibility

This slip-on is a direct replacement for the standard silencer on the following model:

• KTM RC 390 — model years 2017, 2018, 2019, 2020

Installation requires the Arrow connecting pipe 71667MI (sold separately). Without this link pipe the slip-on will not fit the OEM header. For a full exhaust conversion, the 71860AK can be combined with an Arrow header to replace the entire system from the cylinder head back.

Please note: the primary product image has been composited for illustrative purposes as Arrow had not released a dedicated photograph for the RC 390 fitment at the time of listing. The product itself is exactly as described here and carries the full Arrow specification for part number 71860AK.

Specifications

• Part number: 71860AK
• Weight: 2.03 kg
• Canister material: aluminium
• End cap material: carbon
• Internal components: stainless steel
• Canister length: 270 mm
• Inlet diameter: 54 mm
• Outlet diameter: 50 mm
• Road approval: E-number type approved
• DB killer: included (fitted as standard)
• Required link pipe: Arrow 71667MI (sold separately)