The DH-35i and DH-40i have evolved into very similar products but they started from different viewpoints.  For both products, the end goal was microscopic imaging of cell cultured surfaces with both temperature and environment control, and with continuous perfusion. 

a. The DH-35i is specialized for controlling the environment and temperature of 35 mm cell culture dishes. Perfusion control is achieved with this microincubator with the added use of an RC-37(W/F) perfusion insert. 

The DH-25i is comprised of three metal sections: the base, a side-wall ring, and the top. This design allows the user to easily remove the top while keeping the perfusion lines and heat reservoir in place.

b. The DH-40i is specialized for controlling the environment and temperature of our Series 40 chambers.  These chambers all use round coverslips. The DH-40i, however, can also be used to study samples held in 35 mm dishes. 

The DH-40i is comprised of two metal sections: the base and the side/top assembly. In this design, opening the incubator removes both the side and top from the culture dish. This permits quick and easy exchange of the sample holder while not disturbing the placement of perfusion and gas lines.
Entry into the incubator can be achieved, however, without removing the side walls by opening the glass window on the incubator top.