Neutral density filter (ND) with an attenuation factor of 4, or simply ND4
Bu Xiangzhi (2607) – Krishnan Sasikiran (2657), Dos Hermanas Internet Chess Club 2005; D85
1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.cxd5 Nxd5 5.Na4 e5 6.dxe5 Nc6 7.a3 Nxe5 8.e4 Nb6 9.Qxd8+ Kxd8 10.Bg5+ Be7 11.0-0-0+ Ke8 12.Bf4 Bd6 13.Nxb6 axb6 14.Kc2 Bd7 15.Bxe5 Bxe5 16.Nf3 Bf6 17.Bc4 Ba4+ 18.Bb3 Bc6 19.Bd5 Ke7 20.e5 Bg7 21.Bxc6 bxc6 22.Nd4 c5 23.Nc6+ Ke6 24.f4 Ra4 25.g3 b5 26.Rhe1 Rha8 27.Nd8+ Ke7 28.e6 f5 29.Rd7+ 1–0