Sapim nipple washers of all sorts for every wheelbuilding need. Round washers reinforce rims (9.0mm diameter, 0.5mm thick). Oval washers do the same (9.0×13.0mm oval, 0.5mm thick). Polyax washers (7.5mm diameter, 0.7mm thick) offer less reinforcement but have a cup profile that matches Sapim Polyax nipples for low friction and improved nipple rotation. Polyax fit all rims.
Spoke length must be increased by adding washer thickness. You may also build washers into spoke length calculations by adding the thickness of two washers to ERD. (Similarly if you find yourself dealing with over length spokes, rebuild with washers for some adjustment.)
Normally ships in 24 hours.