A matched pair of Germanium AC187K and AC188K transistors from RS Components. Download shortform AC187 / 188 datasheet: RS legacy Stock number 294-154 Each come already mounted in a big aluminium block (7 x 7 x 15mm) which can be bolted down using an M2.5 bolt. (see photo) Status: NOS (New Old Stock) Tested component: YES RoHS: no