Collet ER, according to standard DIN 6499, form B, type class 2, size ER 40. Brand Gurfer with reference ER40-2.
Also available: set of ER collets, DIN 6499 B CL2, size ER 40, Ø 4,0 - 26,0 mm per 1 mm, 23-piece, in plastic storage case (ref. ER40SET2).
For mounting tools with straight shank.