Accuracy Solutions Baby Orcas/ Mama Orcas/ Makos Chassis Arca Rail Black CHS ARCA RAIL. It can also be installed at the bottom of the fore-end and on the sides of the barrel channel as those hole patterns are identical. ATTENTION: Your Mako or Orca chassis may be fitted with either 10-24 or 10-32 threads. Please ensure you perform a gentle thread test before attempting installation. Specifications for Accuracy Solutions Baby Orcas/ Mama Orcas/ Makos Chassis Arca Rail: Manufacturer: Accuracy Solutions Color: Black Finish: Type III Hardcoat Anodizing Gun Rail: Arca Package Contents: Accuracy Solutions Baby Orcas/ Mama Orcas/ Makos Chassis Arca Rail Accuracy Solutions CHS ARCA RAIL 10-32: Baby Orcas/ Mama Orcas/ Makos Chassis Arca Rail Black