M8 x 13 11.0 - 11.5 mm. M8 x 20 11.0 - 11.5 mm. M8 x 25 11.0 - 11.5 mm. Insert Nuts provide a strong, permanent thread for wood and wood based sheet materials. The unique external thread ensures strong resistance against pull out and the flanged head of D-Type inserts prevents splitting of the surfaces and driving the Insert in too far.
eBay