1/2" CLOSED SPOON, RYAN 522361, BLUE BIRD 71910, FITS MODEL LAWNAIRE IV, 7-5/8"L, CLASSEN. 0.090 O.D. 30 Required For a Complete Lawnaire IV Plus Aerator Set, 42 Required For a Complete Lawnaire V Plus Aerator Set. Fits Blue Bird models 424, 530A and 742 Replaces: BLUEBIRD 71910