These are matched sets (pairs) of left and right side-rails for Peter Lynn kite buggies.  Made of welded stainless steel.
These are non-stock at CWS and are special ordered.  We have an order coming over the Pond from Peter Lynn in Europe about every 2-4 weeks and can bring a pair over for you with the next shipment.

Note:  All XR+ and Bigfoot frame parts are interchangeable.  For example, you can swap out XR+ side-rails with Bigfoot+ side-rails to add about 6" (15 cm) length (In which case we suggest also adding a Bigfoot downtube to maintain weight distribution).