Distance between bottom nozzle and focus lens

[Techsavvy34]

I was wondering if anybody off hand knows what the distance from the focus lens to the bottom of the nozzle is on this Laser head- LSR-LH1820B

[cefs]

28.5mm according to the poster who commented on it on its web page. He says 50.8 focal length and had 20.3 clearance between tip and object on bed. This is not guaranteed but a guess based on his info.