NOVELTY - A rubber composition comprises copolymer (A) of ethylene, 3-20C ( alpha )-olefin and non-conjugated polyene, silane-containing compound (B) and methacrylic acid ester compound (IV)-(IX). The copolymer (A) has ethylene unit and ( alpha )-olefin unit in the mass ratio of 35/65-95/5, iodine number of 0.5-50 and intrinsic viscosity ( eta ) in decalin solution at 135 degrees C of 0.01-5.0 dl/g. The compound (B) is chosen from compound (II) having two silane groups in a molecule and compound (III) having three silane groups in a molecule.    USE - Rubber composition for gasket for fuel cells and sealing material (all claimed).    ADVANTAGE - The rubber composition has excellent heat resistance, acid resistance, gas permeability proof property, high speed forming property and produces molded products with low hardness, excellent high temperature compression set and low counter force. The composition does not adhere to the metal mold.    DETAILED DESCRIPTION - A rubber composition comprises copolymer (A) of ethylene, 3-20C ( alpha )-olefin and non-conjugated polyene, silane-containing compound (B) and methacrylic acid ester compound chosen from formulae: CnH2n(-O-C(=O)-C(-CH3)=CH2)2 (IV), H2C=C(-CH3)-C(=O)-O-(C2H4O)n'-C(=O)-C(-CH3)=CH2 (V), H2C=C(-CH3)-C(=O)-O-(C2H4O)n"-CH3 (VI), 2-methyl-acrylic acid benzyl ester and formulae (VIII) and (IX). The copolymer (A) has ethylene unit and ( alpha )-olefin unit in the mass ratio of 35/65-95/5, iodine number of 0.5-50 and intrinsic viscosity ( eta ) in decalin solution at 135 degrees C of 0.01-5.0 dl/g. The compound (B) is chosen from compound (B1) of formula: H-Si(-R3)2-(O-Si(-R3)2)a-R4-(Si(-R3)2-O)b-Si(-R3)2-H (II) having two silane groups in a molecule and compound (B2) of formula (III) having three silane groups in a molecule.    R3,R5=1-10C monovalent group, preferably optionally substituted saturated hydrocarbyl or aryl;    a-c=0-20;    R4=1-30C bivalent organic group or O;    R6=1-30C trivalent organic group;    n=1-5;    n'=1-4;and    n",m,o=1-10.