 The fruit body of Suillus collinitus is a medium to large, fleshy bolete. The cap is initially rounded, becoming convex and finally flat, reaching up to 11 cm (4.3 in) in diameter. The cap is covered with a brown cuticle of variable shade that is decorated with minuscule radial striations, which become more obvious in fully expanded specimens and especially in dry weather. The cap is often shaped irregularly and becomes viscid (sticky) when damp. The tubes are short and their stem attachment is usually slightly decurrent to adnate. The small and angular pores are yellow but darken with age. Young, fresh specimens sometimes bear droplets of a clear fluid that collect on the pore surface.
