The Reimax down pipe comes in three versions. The 60mm version, the 65mm version, and the titanium version.
From the Reimax website about all three.
The 60mm version:
"Considering engine pulsation, the length of the pipe to the assembly is designed to be the same. Since the pipe diameter is 60φ x 2 to 70φ and the exhaust pressure is taken into consideration, the response of the engine is improved and it blows up smoothly from low rotation to high rotation."
Main diameter: 60φ x 2 to 70φ
Material: SUS304 stainless steel Applicable
The 65mm version:
"By setting the outer diameter of the pipe to 65φ in consideration of the exhaust pressure, we have achieved an improvement in peak power without impairing the torque in the low speed range compared to the general 70φ type. It brings out the performance of the RB26 further and demonstrates the best performance. It is a pipe layout that considers the balance between isometric length and minimum ground clearance."
Main diameter: 65 x 2 (flange inner diameter 70φ) -80φ
Material: SUS304 stainless steel
The Titanium version:
"We pursued lightness and tone. It weighs only 2.1 kg and is lightweight. Please enjoy the high-pitched tone from around 3,000 rpm.The pipe layout is the same as the all-stainless steel front pipe (17401-AAR10)."
Main diameter: 60.5 × 2 ～ 70φ