I was constantly looking for this information, so here you go. Perhaps it will help you turn a $10 brush or brush handle into something you will use indefinitely. Omega Brushes By Knot Size Ht x Loft x Base x Knot Knot/Loft 18mm Knot Omega 10086 88x42x46x18 18/46 Omega 20086 88x46x42x18 18/46 Omega 50068 74x46x28x18 18/46 19mm Knot Omega 63184 97x53x54x19 19/53 20mm Knot Omega 21047 73x43x30x20 20/43 Omega 10015 96x49x47x20 20/49 Omega 63171 92x50x42x20 20/50 Omega 63173 92x50x42x20 20/50 21mm Knot Omega 50014 90x45x45x21 21/45 Omega 13522 93x46x47x21 21/46 Omega 10099 100x48x52x21 21/48 Omega 10275 93x48x45x21 21/48 Omega 40099 100x48x52x21 21/48 Omega 11130 114x49x65x21 21/49 Omega 90075 95x49x46x21 21/49 Omega 63325 101x50x51x21 21/50 Omega 90077 98x50x48x21 21/50 Omega 10290 105x51x54x21 21/51 Omega 11648 105x51x54x21 21/51 Omega 63183 94x51x43x21 21/51 Omega 66229 105x54x51x21 21/54 Omega 66230 110x56x54x21 21/56 22mm Knot Omega 10075 94x49x45x22 22/49 Omega 13564 96x49x47x22 22/49 Omega 90072 104x49x55x22 22/49 Omega 90081 104x49x55x22 22/49 Omega 10077 98x50x48x22 22/50 Omega 10072 105x51x54x22 22/51 Omega 10218 103x51x52x22; 22/51 Omega 10219 103x51x52x22; 22/51 Omega 63185 100x51x49x22 22/51 Omega 80056 100x51x49x22 22/51 Omega 91087 104x51x53x22 22/51 Omega 13111 103x52x51x22 22/52 Omega 63188 107x53x54x22 22/53 Omega 63167 109x54x55x22 22/54 Omega 33174 103x55x48x22 22/55 Omega 66149 111x55x56x22 22/55 Omega 643167 110x55x55x22 22/55 Omega 31232 112x56x56x22 22/56 Omega 63164 104x56x48x22 22/56 Omega 63181 108x56x52x22 22/56 Omega 81229 106x56x50x22 22/56 Omega 643174 104x56x48x22 22/56 Omega 646150 112x56x56x22 22/56 23mm Knot Omega 40033 88x48x40x23 23/48 Omega 90005 105x49x56x23 23/49 Omega 10018 103x50x53x23 23/50 Omega 10019 103x50x53x23 23/50 Omega 81056 100x50x50x23 23/50 Omega 90018 103x50x53x23 23/50 Omega 90051 93x50x43x23 23/50 Omega 90065 100x50x50x23 23/50 Omega 10051 93x51x42x23 23/51 Omega 63186 105x52x53x23 23/52 Omega 33176 106x53x53x23 23/53 Omega 63162 103x53x50x23 23/53 Omega 13109 104x54x50x23 23/54 Omega 31241 110x54x56x23 23/54 Omega 33175 107x54x53x23 23/54 Omega 343312 115x54x61x23 23/54 Omega 10810 109x55x54x23 23/55 Omega 11137 113x55x58x23 23/55 Omega 11148 105x55x50x23 23/55 Omega 63187 109x55x54x23 23/55 Omega 80257 95x55x40x23 23/55 Omega 80266 105x55x50x23 23/55 Omega 10081 109x56x53x23 23/56 Omega 10105 114x56x58x23 23/56 Omega 11573 106x56x50x23 23/56 Omega 11574 106x56x50x23 23/56 Omega 11575 106x56x50x23 23/56 Omega 31231 111x56x55x23 23/56 Omega 46113 110x56x54x23 23/56 Omega 63180 113x56x57x23 23/56 Omega 80280 109x56x53x23 23/56 Omega 81052 106x56x50x23 23/56 Omega 81230 109x56x53x23 23/56 Omega 80265 105x56x49x23 23/56 Omega 643188 110x56x54x23 23/56 Omega 31073 109x57x52x23 23/57 Omega 10029 103x59x53x23 23/59 Omega 11150 115x59x56x23 23/59 24mm Knot Omega 80267 104x44x49x24 24/44 Omega 643186 106x51x55x24 24/51 Omega 11121 104x52x52x24 24/52 Omega 10065 105x54x51x24 24/54 Omega 10066 105x54x51x24 24/54 Omega 10005 110x55x55x24 24/55 Omega 11126 115x55x60x24 24/55 Omega 11205 108x55x53x24 24/55 Omega 81054 111x55x56x24 24/55 Omega 66231 112x55x57x24 24/55 Omega 66232 112x55x57x24 24/55 Omega 80097 106x55x51x24 24/55 Omega 90103 114x55x59x24 24/55 Omega 40652 106x56x50x24 24/56 Omega 81569 109x56x53x24 24/56 Omega 80005 111x56x55x24 24/56 Omega 640652 106x56x50x24 24/56 Omega 63169 114x57x57x24 24/57 Omega 63170 114x57x57x24 24/57 Omega 21139 118x60x58x24 24/60 Omega 80067 109x60x49x24 24/60 25m Knot Omega 290049 121x57x64x25 25/57 Omega 343178 111x57x54x25 25/57 Omega 346235 112x57x55x25 25/57 Omega 31156 115x58x57x25 25/58 Omega 31020 113x59x54x25 25/59 Omega 31025 113x59x54x25 25/59 Omega 31064 113x59x54x25 25/59 Omega 63178 112x59x53x25 25/59 Omega 50107 125x68x67x25 25/68 Omega 80080 112x58x54x25 25/58 26mm Knot Omega 46186 108x54x54x26 26/54 Omega 46151 110x56x54x26 26/56 Omega 646186 108x54x54x26 26/54 Omega 10083 128x64x64x26 26/64 27mm Knot Omega 10104 113x55x58x27 27/55 Omega 71278 114x60x54x27 27/60 Omega 20102 121x64x57x27 27/64 Omega 20248 128x64x64x27 27/64 Omega 10049 128x65x63x27 27/65 Omega 10098 145x65x80x27 27/65 Omega 20106 135x66x67x27 27/66 Omega 20480 132x69x63x27 27/69 28mm Knot Omega 10048 133x70x65x28 28/70
Great resource @Rev579! I do like the feel of Omega knots and have used one as a replacement. Some have relatively cheap plastic handles that can be thrashed and tossed when harvesting the knot as a donor for a restoration.
I have an 83 and a 49. Always assumed they were the same knot, but the 49 is actually bigger. You learn something every day.