Spot rubber strengthened further catalysed by the sustained gains in futures on Tuesday. Supply concerns owing to widespread rains and covering purchases at lower levels kept the sentiments bullish during late trading hours. RSS 4 improved to ₹135 (₹133) a kg, as quoted by the traders. The grade firmed up to ₹133.50 (₹130.50) and ₹130.50 (₹127.50) respectively, according to the Rubber Board and the dealers. June futures firmed up to ₹135.10 (₹132.74), July to ₹135.88 (₹133.54), August to ₹135.18 (₹132.95) and September to ₹134 (₹131.54) on the National Multi Commodity Exchange. RSS 3 (spot) closed at ₹102.35 (₹102.17) at Bangkok. June futures closed at ¥157.1 (₹97.32) on the Tokyo Commodity Exchange. Spot rubber rates (₹/kg): RSS-4: 135 (133); RSS-5: 131 (129); Ungraded: 114 (112); ISNR 20: 113.50 (113) and Latex (60% drc): 96 (95).