This is a rear Wheel Cylinder for a Austin Healey BN7-BJ8 and TR3A from TS15332 to TS34403 with 3/4" with a slotted wheel cylinder pistons Made in Italy by AP Braking. Or can be used for more rear braking in a Triumph TR4,4A, TR250 and TR6, call for details. Cross reference 390416 and GWC1118 021-151