Lewmar Plastic Upstand Cup is often worn and breaks fairly easy when exposed to weather and sunlight. A perfecty solution is to replace the Plastric Cup with Lewmar new Stainless Upstand Cup.
Please check your correct size:
Size 1 = Bolt Diameter 9mm
Size 2 = Bolt Diameter 13mm
Size 3 = Bolt Diameter 17mm
(The "Bolt" Diameter refers to the SQUARE opening/hole at the top of the Stainless Cup, NOT the two smaller round openings which is for the locking pin.)