Chop Saw Spider from Porkchop BMX - classic styling, modern quality, and made in the U.S.A. * Model: The "RETRO"  * Color: RED ANODIZED * Weight: 67g * Material: 6061 aluminum alloy * Chainring interface: 110 bcd (Don't know what size Bolt Circle Diameter your existing chainring is? Measure center-to-center of two adjacent bolt holes on your chainring and then refer to this chart: http://www.sheldonbrown.com/cribsheet-bcd.html ) * Crank spindle size: 23.75mm (for one piece cranks) - if you want to run this on a 3-piece crank, you will need an adapter. Keep in mind, 3 piece crank spindles can be 19mm, 20mm and 22mm - so be sure you measure your spindle to be sure you get the correct adapter. * MADE IN THE USA IMPORTANT - PLEASE READ: Chain alignment is unbelievably important for both YOUR SAFETY and performance/smoothness of the drivetrain. Because of this, we highly recommend all drivetrain products such as this be installed by a professional bicycle mechanic. If you choose to install this product yourself, be sure the chain is in exact alignment between the rear sprocket and the front sprocket. This spider is made symmetrical to allow for you to mount a chainring on either the front side or backside depending on what works best for your rear cog alignment. For 3 piece sealed bearing cranks you may also need to shim using spacers. For one piece cranks or loose ball 3 piece cranks your only additional adjustment is to space the rear wheel to bring the rear sprocket into alignment. Unfortunately, drivetrain components are not plug and play. This is because there are 100's of wheel hubs, cranks, frames, spiders/power discs, chainrings/wheels, etc. that have been made over the past 30 years of BMX and making all of it work together takes proper installation and adjustment.