These are a Genuine Annovi Reverberi ceramic piston kit.  Comes with 3 pistons.

See below for list of pumps the various kits are suitable for:

18mm (Kit 2746) - XMA 4 G20 (7958), SXM 13.20 (21255), SXM 15.20 (21256), XM 13.17 (7938), XM 15.15 (7942), XM 13.17 (7902), XM 15.15 (7906), SXMA 4 G30 (21261), XMA 4 G20 (7922), SXM 13.20 (21267), SXM 15.20 (21265), HRR 15.15 ET (23978), HRR 15.20 ET (23979), HRR 18.16 ET (23980), RR 13.20 (23775), RR 15.15 (23776), RR 15.20 (23777), RR 18.16 (23778), RR 13.20 (23771), RR 15.25 H (24934), RR 15.15 (23772), RR 15.20 (23507), RR 18.12 (23773), RR 18.16 (23774), RRA 3 G30 (23782), RRA 3.5 G30 (24565) f.c., RRA 4 G30 (23783), RRA 5.5 G26 (23784), RRA 3.5 G25 (23779), RRA 4 G30 (23780), RRA 4 G36 H (24937), RRA 5.5 G30 (23781), HYD - XM 15.15 (21603), HYDRAULIC DRIVE XM 15.15 (21598), HSXM 13.20 ET (21370) ,HSXM 15.20 ET (21371), HXM 13.17 ET (20196), HXM 15.15 ET (20197)

20mm (Kit 2650) - CWX 15.17 (20472), CWX 18.10 (20473), CWX 15.17 (20474), XWA 4 G20 (20781), XWA 4 G30 (20354), XWA 5.5 G22 (20180), XWA 5.5 G30 (20061), XWA 5.5 G40 (21138), XWA 7 G22 (20181), XWA 7 G32 (20062), XWA 7 G35 (21139), XWA 7 G40 (21140), XWA 8 G19 (20182), XWA 8 G29 (20063), XWA 8 G35 (21141), XW 15.15 (20352), XW 15.20 (20353), XW 15.30 (20592), XW 21.20 (20714), XW 21.25 (20058), XW 21.28 (21136), XW 26.12 (20175), XW 26.15 (20176), XW 26.20 (20059), XW 26.23 (20177), HXWA 4 G20 ET (20782), HXWA 4 G30 ET (20783), HXW 15.15 (20871), HXW 15.20 (20872), HXW 21.20 (20224), HXW 26.15 (20225)

22mm (Kit 1891) - WHW 15.20 (22986), WHW 21.15 (22987), WHW 26.15 (22988), WHW 32.20 (22989), XWA 9 G16 (20183), XWA 9 G24 (20064), XWA 9 G30 (21645), XW 30.10 (20178), XW 30.15 (20179), XW 30.20 DX (20060), XW 30.20 SX (20270), XW 30.25 (21137), HYDRAULIC DRIVE XW 30.10 (21601), HYDRAULIC DRIVE XW 30.15 (22318), HYD - XW 30.10 (21606), HYD - XW 30.15 (22694), HXW 30.10 (20227), HXW 30.15 (20228), HXW 30.20 (20229), GEARBOX DRIVE XW 30.15 (20241)

28mm (Kit 1849) - XWLA 13 G15 (21198), XWT 21.18 (21048), XWT 21.20 (22994), XWL 36.15 (22175), XWL 41.20 (22462), XWL 42.05 (21057), XWL 42.07 (21058), XWL 42.10 (21059), XWL 42.15 (21060), XWL 50.15 (23709), XWL 50.15H (23816), XWF 26.06 (21049), XWF 26.09 (21050), XWF 26.12 (21051), XWF 26.15 (21052), XWF 26.20 (21053), XWF 30.10 (21054), XWF 30.18 (21055), XWF 30.20 (22921), XWF 36.17 (21056), HYD - XWL 50.09 (25049), HXWL 42.07 ET (21183), HXWL 42.10 ET (21184), HXWL 42.04 ET (24960) F.C, WHWL 38.15 (23966), WHWL 42.15 (23967), WHWL 50.15 (23968).