New video from MadBull Airsoft... "The Ultimate ball bearing spring guide features a slightly thinner diameter shaft to accommodate springs of all sorts, making it more forgiving for both the spring and piston to compress.  The spring guide's shaft is built-in with the top bearing plate to allow more rigidity and maximum spring decompression.  As a spring decompresses, the bearings allow full twisting, adding improved rounds-per-second and maximum power.