These are ME threaded Ross pop adjustable safety valves.
5/8" x 26tpi & 1/2" x 26tpi B1 Type (2" tall x 18mm hexagon)
Rob Roy type available in 1/8 BSP, 3/8 x 32tpi, 3/8 x 26tpi, 5/16 x 32tpi & 5/16 x 26tp (1 1/2" tall x 1/2" diameter)
These are manufactured items, so please allow up to 7 days for delivery.