\begin{tikzpicture}[very thick, scale=1, font={\footnotesize\sffamily}]
%\draw[help lines,xstep=.5,ystep=.5] (-7,-3) grid (7, 3);
\node (assambly) at (0,0) {\includegraphics[width=0.66\textwidth]{Fibres/figures/single_explode_Holder_mod}};
%\node[rotate=-90] (fibres) at (-6.5,0.5) {\includegraphics[width=2.5cm]{roundFibres}};

\draw[thick, <->] (-2.0, 1.4) -- (-2.0, -1.2);
\node[rotate=-90, anchor=north] at (-1.95, 0.4) {$\sim$\SI{32}{\milli\meter}}; 
\draw[thick, <-] (-4.5, -1.3) -- +(0.4, -0.3);
\node[anchor=west, align=left] at (-4.1, -1.6) {$\sim$\SI{1}{\milli\meter}};
\node[seaborndeep1] at (-2.7, 1.7) {fibre ribbon};
\node[align=center,anchor=south] at (-1.2, 2.0) {holding\\ structure}; 
\draw[thick, ->] (-1.2,2.0) -- (-0.7, 1.0);
\node[align=center,anchor=south] at ( 1.4, 2.0) {flex print\\ cable}; 
\draw[thick, ->] (1.4, 2.0) -- (1.1, 1.0);
\node[align=center,anchor=north] at ( 0.5, -2.0) {SiPM column\\ array}; 
\draw[thick, ->] (0.5, -2.0) -- (1.0, -1.5);
\node[align=center,anchor=north] at ( 3.5, -2.0) {stiffener \&\\ spring loading}; 
\draw[thick, ->] (3.5, -2.0) -- (3.0, -1.0);
\node[anchor=west] at (3.2, 0.5) {3 x screws};
\draw[thick, <->] (-1.15, -0.8) -- (-6, -0.86);
\node[anchor=south, align=center, rotate=0] at (-4.1,-0.85) {$\sim$\SI{29}{\centi\meter}};

\end{tikzpicture}