This is a 175mm pair of our titanium cranks, acid washed using a 12 hour process, and then anodized to 72.5V to acheive a "blurple" finish that looks blue or purple depending on the angle and lighting. The acid washing process is something we've been experimenting with, and this is the first pair we've offered to the public. They are potentially one-of-a-kind.

Full description from our titanium cranks product page:

Carefully machined from 6Al-4V "Grade 5" titanium and featuring a novel split lattice design, these crank arms have an incredible strength-to-weight ratio. Each of these 175 crank arms weigh around 8oz. Although there are lighter cranks on the market, fatigue and impact testing at ACT Labs in Long Beach, CA showed that these crank arms in particular remain durable even as titanium spindles and standard BMX pedals begin to fail. What this means is that after repeated abuse, you'll more likely need to replace your spindle, bottom bracket bearing, and/or pedal long before you'll need to replace one of these crank arms. You can read all about the initial development of these cranks on our blog, and watch a mashup video of crank testing on our youtube. You can see a full installation video here. Please note that if you use a Profile Column crank installation tool, it may require some additional spacers on the tool to install these cranks. 

Material: 6Al-4V "Grade 5" titanium
Spindle: 22mm 48 spline
Spindle widths: 143 (BMX) or 160mm (MTB)
Bolts: M17x1.25, 10mm hex
Drive: Spline-drive only (compatible with all 22mm/48 splined sprockets)
Weight:
600g/21.1oz = 170mm arms, bolts, bolt washers, and 143mm spindle
618g/21.8oz = 170mm arms, bolts, and 160mm spindle

Spline-drive sprocket weight:
25t = 72g/2.54oz
28t = 90g/3.17oz
34t = 101g/3.56oz